Aims. To determine whether there is any benefit using a minimally invasive trans-sartorial approach as described by Professor Søballe compared to the ilio-femoral for peri-acetabular osteotomy. Methods. 30 consecutive patients were operated on by a single surgeon. The first 15 underwent an ilio-femoral (I-F) approach whilst the following 15 had a trans-sartorial (T-S) approach. Fixation was achieved with 3 or 4 screws. All other aspects of surgery and rehabilitation were the same. Data was collected prospectively and included operation time, intra-operative blood loss and length of stay. Acetabular correction was measured using the sourcil and centre edge angle (CEA) on pre and post-operative radiographs. Results. Both groups had acceptable radiographic corrections with CEA improving from mean 14.5 to 38.7 degrees (T-S) and 14 to 39 degrees (I-F). The sourcil angle improved from mean 17.8 to 2 degrees (T-S) and 19.5 to −1.5 (I-F). Minimally invasive surgery reduced anaesthetic time by 62 minutes. Haemoglobin loss was reduced by 1 gram/L and there was no requirement for transfusion. Hospital stay reduced by 0.8 days. There were no major adverse complications although two partial femoral neurapraxias were noted early in the series. These fully resolved. Conclusion. We have found significant benefit from changing to minimally invasive PAO. Our patients have smaller wounds, a shorter operative time, reduced bleeding and a shorter length of stay. We found no adverse effects. The time savings have also corresponded to a cost saving for our institution. We recommend this technique although recognise that it has a learning curve and should be initiated by surgeons with previous PAO experience

Periacetabular osteolysis is seen in response to particles (polyethylene, ceramic, metal or cement), at times in the presence of an unstable implant, and perhaps made worse by the unique host response to the particle burden. The impact of wear modes: due to either the primary bearing surface (MOP, MOM, COC) or unintended surfaces as seen in impingement, as well as the quality of the bearing counterface all influence the extent of the osteolytic response. The final common pathway appears to be via macrophage stimulation, an upregulation of cytokines leading to a resorption of bone.

The patterns of lysis range from linear resorption at the implant interface to more expansile patterns which can be more dramatic in size and may place the implant at jeopardy for loosening. Assessment of implant fixation as well as extent of the lytic process employs the use of plain radiographs (including oblique views), computerised tomography and magnetic resonance imaging. The utility of MRI for the quantification of bone loss as well as the newer phenomena of associated soft tissue lesions (pseudotumors, adverse tissue reactions) has turned out to be a valuable tool in helping determine timing and need for revision.

The basic principles in determining need for revision surgery revolve around: degree of lysis, integrity of the soft tissues, fixation of the implant, track record of the implant, as well as patient factors including symptoms, age and activity.

In cemented sockets, progressive bone loss, pain with or without overt loosening is indication for revision which is generally accomplished using an uncemented hemispherical acetabular component with bone graft and screw augmentation.

In the uncemented socket, the decision to revise is based upon a) implant stability, 2) the integrity of the locking mechanism, 3) degree of bone loss. With stable implants, polyethylene exchange and “lesional” treatment is appropriate. Well fixed implants with extensive lysis can be successfully managed with liner exchange and bone grafting as necessary. If the liner locking mechanism is compromised, cementing a liner into place is an excellent strategy. Removing a well fixed cup with extensive lysis runs the risk of encountering a large acetabular defect which may be difficult to reconstruct. Loose implants clearly require revision.

In the era of “hard bearings”, progressive soft tissue expansion leading to damage of the abductor and other soft tissue constraints about the hip is an indication for revision. Revision of MOM THR's may be performed by maintaining the femoral component and performing an isolated acetabular revision or in some instances of modular acetabular components, maintaining the shell and inserting a new liner. In all instances of implant retention, it is critical to confirm that the components are in optimised position: implants retained in suboptimal position are at risk for early failure.

With cementless porous-coated acetabular replacements, extensive bone loss can occur without effecting implant stability. As a result, the surgeon is frequently faced with re-operating on a well-fixed cementless acetabular component with osteolysis and must decide whether or not to remove a well-fixed porous coated socket. A classification system and treatment algorithm has been developed to aid in management decisions regarding re-operation for polyethylene wear and pelvic osteolysis.

Cases are classified into one of 3 possible categories depending on the radiographic stability of the porous coated shell and the ability to replace the polyethylene liner. Type I case; stable porous coated shell, liner replaceable; Type II case; socket stable, liner not replaceable;

Type III case; socket loose, not osseointegrated.

Treatment Algorithms - Retain well-fixed shell in Type I cases and replace the liner. Debride accessible lytic lesions and graft with allograft chips. Remove the well-fixed shell in Type II case. Assess defect once the shell is removed. Reconstruction based on the bony defect present. The vast majority can be revised with a larger porous coated socket. Remove loose socket in Type III cases. Assess defect and reconstruct based on the defect. There is a greater need for more extensive grafting and the use of reconstruction rings with Type III cases.

This treatment algorithm has helped the authors successfully evaluate and treat a large series of patients with polyethylene wear and pelvic osteolysis in association with porous coated acetabular components. The stability of the acetabular component and appropriate knowledge of the implant are important factors that impact surgical management.

With cementless porous-coated acetabular replacements, extensive bone loss can occur without affecting implant stability. As a result, the surgeon is frequently faced with re-operating on a well-fixed cementless acetabular component with osteolysis and must decide whether or not to remove a well-fixed porous coated socket. A classification system and treatment algorithm has been developed to aid in management decisions regarding re-operation for polyethylene wear and pelvic osteolysis.

Cases are classified into one of 3 possible categories depending on the radiographic stability of the porous coated shell and the ability to replace the polyethylene liner. Type I case; stable porous coated shell, liner replaceable; Type II case; socket stable, liner not replaceable; Type III case; socket loose, not osseointegrated

Relative Contra-indications for Liner Exchange – Type II Case - Malpositioned socket, Severely damaged shell or lock detail (consider cementing shell in place), Poor track record of the implant, Highly crosslinked polyethylene liner of adequate thickness not available, Ongrowth (as opposed to ingrowth) fixation surface

Treatment Algorithm

Type I Case: Retain well-fixed shell in Type I cases and replace the liner. Debride accessible lytic lesions and graft with allograft chips.

Type II Case: Remove the well-fixed shell in Type II case. Assess defect once the shell is removed. Reconstruction based on the bony defect present. The vast majority can be revised with a larger porous coated socket.

Type III Case: Remove loose socket. Assess defect and reconstruct based on the defect. There is a greater need for more extensive grafting and the use of reconstruction rings with Type III cases.

This treatment algorithm has helped the authors successfully evaluate and treat a large series of patients with polyethylene wear and pelvic osteolysis in association with porous coated acetabular components. The stability of the acetabular component and appropriate knowledge of the implant are important factors that impact surgical management.

Polyethylene and femoral head exchange for wear or osteolysis is a common operation. The difficulty lies in the facts that wear and osteolysis are difficult to measure, wear does not always correlate with osteolysis, catastrophic failure (wear through, loosening, or fracture) is difficult to predict, and these problems are usually asymptomatic.

I currently recommend this procedure when complete wear through of the polyethylene is present or impending, when the patient has obvious wear and symptoms, or if there is a rapidly enlarging osteolytic lesion.

The surgical goals focus on management of debris generation and management of the osteolytic lesion. A third goal becomes avoidance of the know complications of this procedure. Management of debris generation basically involves modernising the head and polyethylene. Management of the osteolytic lesion includes debridement and when possible grafting. By far the most common complication after this procedure is dislocation. Prevention of dislocation should be accomplished by patient education, use of larger heads when possible, and capsular repair.

Prerequisites to perform this procedure are a replacement liner of adequate thickness that can be locked or cemented in place. The acetabular component must be stable. Lastly the component must be properly oriented to minimise both wear and dislocation.

Metal-on-metal liner conversion to metal-on-poly is becoming more common. Since patient satisfaction with THA is high, MoM patients may unknowingly minimise their symptoms because they are minor compared to the symptoms before surgery. The patient history should include specific questions about groin pain, swelling, hip noise, and asking the patient if they notice their hip on a daily basis. Patient symptoms, osteolysis and a pseudotumor are indications for modular conversion. Radiographically stable, well-oriented components that can accept a polyethylene liner are requirements for a successful conversion.

Polyethylene and femoral head exchange for wear or osteolysis is a common operation. The difficulty lies in the facts that wear and osteolysis are difficult to measure, wear does not always correlate with osteolysis, catastrophic failure (wear through, loosening, or fracture) is difficult to predict, and these problems are usually asymptomatic.

I currently recommend this procedure when complete wear through of the polyethylene is present or impending, when the patient has obvious wear and symptoms, or if there is a rapidly enlarging osteolytic lesion.

The surgical goals focus on management of debris generation and management of the osteolytic lesion. A third goal becomes avoidance of the know complications of this procedure. Management of debris generation basically involves modernising the head and polyethylene. Management of the osteolytic lesion includes debridement and when possible grafting. By far the most common complication after this procedure is dislocation. Prevention of dislocation should be accomplished by patient education, use of larger heads when possible, and capsular repair.

Prerequisites to perform this procedure are a replacement liner of adequate thickness that can be locked or cemented in place. The acetabular component must be stable. Lastly the component must be properly oriented to minimise both wear and dislocation.

The reconstruction of peri-acetabular defects after severe bone loss or pelvic resection for tumor is among the most challenging surgical intervention. The Lumic® prosthesis (Implantcast, Buxtehude, Germany) was first introduced in 2008 in an effort to reduce the mechanical complications encountered with the classic peri-acetabular reconstruction techniques and to improve functional outcomes. Few have evaluated the results associated with the use of this recent implant. A retrospective study from five Orthopedic Oncology Canadian centers was conducted. Every patient in whom a Lumic® endoprosthesis was used for reconstruction after peri-acetabular resection or severe bone loss with a minimal follow-up of three months was included. The charts were reviewed and data concerning patients’ demographics, peri-operative characteristics and post-operative complications was collected. Surgical and functional outcomes were also assessed. Sixteen patients, 11 males and five females, were included and were followed for 28 months [3 – 60]. Mean age was 55 [17–86], and mean BMI reached 28 [19.6 – 44]. Twelve patients (75%) had a Lumic® after a resection of a primary sarcoma, two following pelvic metastasis, one for a benign tumor and one after a comminuted acetabular fracture with bone loss. Twelve patients (75%) had their surgery performed in one stage whereas four had a planned two-stage procedure. Mean surgical time was 555 minutes [173-1230] and blood loss averaged 2100 mL [500-5000]. MSTS score mean was 60.3 preoperatively [37.1 – 97] and 54.3 postoperatively [17.1-88.6]. Five patients (31.3%) had a cemented Lumic® stem. All patients got the dual mobility bearing, and 10 patients (62.5%) had the largest acetabular cup implanted (60 mm). In seven of these 10 patients the silver coated implant was used to minimize risk of infection. Five patients (31.3%) underwent capsular reconstruction using a synthetic fabric aiming to reduce the dislocation risk. Five patients had per-operative complications (31.3%), four were minor and one was serious (comminuted iliac bone fracture requiring internal fixation). Four patients dislocated within a month post-operatively and one additional patient sustained a dislocation one year post-operatively. Eight patients (50%) had a post-operative surgical site infection. All four patients who had a two-stage surgery had an infection. Ten patients (62.5%) needed a reoperation (two for fabric insertion, five for wash-outs, and three for implant exchange/removal). One patient (6.3%) had a septic loosening three years after surgery. At the time of data collection, 13 patients (81.3%) were alive with nine free of disease. Silver coating was not found to reduce infection risk (p=0.2) and capsuloplasty did not prevent dislocation (p=1). These results are comparable to the sparse data published. Lumic® endoprosthesis is therefore shown to provide good functional outcomes and low rates of loosening on short to medium term follow-up. Infection and dislocation are common complications but we were unable to show benefits of capsuloplasty and of the use of silver coated implants. Larger series and longer follow-ups are needed

The reconstruction of peri-acetabular defects after severe bone loss or pelvic resection for tumor is among the most challenging surgical intervention. The Lumic® prosthesis (Implantcast, Buxtehude, Germany) was first introduced in 2008 in an effort to reduce the mechanical complications encountered with the classic peri-acetabular reconstruction techniques and to improve functional outcomes. Few have evaluated the results associated with the use of this recent implant. A retrospective study from five Orthopedic Oncology Canadian centers was conducted. Every patient in whom a Lumic® endoprosthesis was used for reconstruction after peri-acetabular resection or severe bone loss with a minimal follow-up of three months was included. The charts were reviewed and data concerning patients’ demographics, peri-operative characteristics and post-operative complications was collected. Surgical and functional outcomes were also assessed. Sixteen patients, 11 males and five females, were included and were followed for 28 months [3 – 60]. Mean age was 55 [17-86], and mean BMI reached 28 [19.6 – 44]. Twelve patients (75%) had a Lumic® after a resection of a primary sarcoma, two following pelvic metastasis, one for a benign tumor and one after a comminuted acetabular fracture with bone loss. Twelve patients (75%) had their surgery performed in one stage whereas four had a planned two-stage procedure. Mean surgical time was 555 minutes [173-1230] and blood loss averaged 2100 mL [500-5000]. MSTS score mean was 60.3 preoperatively [37.1 – 97] and 54.3 postoperatively [17.1-88.6]. Five patients (31.3%) had a cemented Lumic® stem. All patients got the dual mobility bearing, and 10 patients (62.5%) had the largest acetabular cup implanted (60 mm). In seven of these 10 patients the silver coated implant was used to minimize risk of infection. Five patients (31.3%) underwent capsular reconstruction using a synthetic fabric aiming to reduce the dislocation risk. Five patients had per-operative complications (31.3%), four were minor and one was serious (comminuted iliac bone fracture requiring internal fixation). Four patients dislocated within a month post-operatively and one additional patient sustained a dislocation one year post-operatively. Eight patients (50%) had a post-operative surgical site infection. All four patients who had a two-stage surgery had an infection. Ten patients (62.5%) needed a reoperation (two for fabric insertion, five for wash-outs, and three for implant exchange/removal). One patient (6.3%) had a septic loosening three years after surgery. At the time of data collection, 13 patients (81.3%) were alive with nine free of disease. Silver coating was not found to reduce infection risk (p=0.2) and capsuloplasty did not prevent dislocation (p=1). These results are comparable to the sparse data published. Lumic® endoprosthesis is therefore shown to provide good functional outcomes and low rates of loosening on short to medium term follow-up. Infection and dislocation are common complications but we were unable to show benefits of capsuloplasty and of the use of silver coated implants. Larger series and longer follow-ups are needed

Aim. We present the long-term surgical outcomes, complications, implant survival and causes of implant failure in patients treated with the modified Harrington procedure using antegrade large diameter pins. Patients and Methods. A cohort of 50 consecutive patients who underwent the modified Harrington procedure along with cemented THA for peri-acetabular metastasis or haematological malignancy between 1990 and April 2018 were studied. The median follow-up time for all patients was 14 years (interquartile range, 9 – 16 years). Results. The 5-year overall survival rate was 33% for all the patients. However, implant survival rates were 100% and 46% at 5 and 10 years respectively. Eight patients survived beyond 5 years. There was no immediate peri-operative mortality or complications. Fifteen late complications occurred in 11 patients (22%). Five (10%) patients required additional surgeries to treat complications. The most frequent complication was pin breakage without evidence of acetabular loosening (6%). Two patients (4%) underwent revision for aseptic loosening at 6.5 and 8.9 years after surgery. Ambulatory status improved in 83%. Conclusions. The modified Harrington procedure for acetabular destruction showed low complication rates, good functional outcome and improved pain relief in selected patients. Long-term results are acceptable in this high risk group of patients. The described procedure using antegrade fully threaded large diameter pins combined with standard arthroplasty showed low rates of complications in this high risk cohort of patients with significant improvement in mobility and pain. This method of reconstruction remains robust for at least 5 years in appropriately selected group of patients

INTRODUCTION. Hip resurfacing offers a more bone conserving solution than total hip replacement (THR) but currently has limited clinical indications related to some poor design concepts and metal ion related issues. Other materials are currently being investigated based on their successful clinical history in THR such as Zirconia Toughened Alumina (ZTA, Biolox Delta, CeramTec, Germany) which has shown low wear rates and good biocompatibility but has previously only been used as a bearing surface in THR. A newly developed direct cementless fixation all-ceramic (ZTA) resurfacing cup offers a new solution for resurfacing however ZTA has a Young's modulus approximately 1.6 times greater than CoCr - such may affect the acetabular bone remodelling. This modelling study investigates whether increased stress shielding may occur when compared to a CoCr resurfacing implant with successful known clinical survivorship. METHODS. A finite element model of a hemipelvis constructed from CT scans was used and virtually reamed to a diameter of 58mm. Simulations were conducted and comparisons made of the ‘intact’ acetabulum and ‘as implanted’ with monobloc cups made from CoCr (Adept®, MatOrtho Ltd, UK) and ZTA (ReCerf ™, MatOrtho Ltd. UK) orientated at 35° inclination and 20° anteversion. The cups were loaded with 3.97kN representing a walking load of 280% for an upper bound height patient with a BMI of 35. The cup-bone interface was assigned a coulomb slip-stick function with a coefficient of friction of 0.5. The percentage change in strain energy density between the intact and implanted states was used to indicate hypertrophy (increase in density) or stress shielding (decrease in density). RESULTS. Implanting both cups changed the strain distribution observed in the hemipelvis, Figure 1. The change in strain distribution was similar between materials and indicated a similar response from the bone, Figure 2. In both implanted cases, the inferior peri-acetabular bone around the implant indicated a reduction in bone strain. The bone remodelling distribution charts show that regardless of threshold remodelling stimulus level (75% in elderly, 50% in younger patients) the CoCr and ZTA cups were expected to produce the same bone response with only a small percentage of the bone in the hemipelvis indicating stress shielding or hypertrophy, Figure 3. DISCUSSION. Currently only metal cups are used for cementless fixation but improvements in design and technology have made it possible to engineer a thin-walled, direct fixation, all-ceramic cup. Both CoCr and ZTA are an order of magnitude greater than the Young's modulus of cortical bone altering the bone strain but changing the material from CoCr to a stiffer ZTA did not change the expected bone remodelling response. Given the clinical history of metal cups without loosening due to bone remodelling, the study indicates that a ZTA cup should not lead to increased stress shielding and is potentially suitable for as a cementless cup for both resurfacing and THR. SIGNIFICANCE. An all-ceramic cup is unlikely to lead to increased stress shielding around the acetabulum due to the change in material. For any figures or tables, please contact the authors directly

Arthrosis of the hip joint can be a significant source of pain and dysfunction. While hip replacement surgery has emerged as the gold standard for the treatment of end stage coxarthrosis, there are several non-arthroplasty management options that can help patients with mild and moderate hip arthritis. Therefore, the purpose of this paper is to review early prophylactic interventions that may help defer or avoid hip arthroplasty. Nonoperative management for the symptomatic hip involves minimizing joint inflammation and maximizing joint mobility through intra-articular joint injections and exercise therapy. While weight loss, activity modifications, and low impact exercises is generally recommended for patients with arthritis, the effects of these modalities on joint strength and mobility are highly variable. Intra-articular steroid injections tended to offer reliable short-term pain relief (3–4 weeks) but provided unreliable long-term efficacy. Additionally, injections of hyaluronic acid do not appear to provide improved pain relief compared to other modalities. Finally, platelet rich plasma injections do not perform better than HA injections for patients with moderate hip joint arthrosis. Primary hip joint arthrosis is rare, and therefore treatment such as peri-acetabular osteotomies, surgical dislocations, and hip arthroscopy and related procedures are aimed to minimise symptoms but potentially aim to alter the natural history of hip diseases. The state of the articular cartilage at the time of surgery is critical to the success or failure of any joint preservation procedures. Lech et al. reported in a series of dysplastic patients undergoing periacetabular osteotomies that one third of hips survived 30 years without progression of arthritis or conversion to THA. Similarly, surgical dislocation of the hip, while effective for treatment of femoroacetabular impingement, carries a high re-operation rate at 7 years follow up. Finally, as the prevalence of hip arthroscopic procedures continues to rise, it is important to recognise that failure to address the underlying structural pathologies can lead to failure and rapid joint destruction. In summary, several treatment modalities are available for the management of hip pain and dysfunction in patients with a preserved joint space. While joint preservation procedures can help improve pain and function, they rarely alter the natural history of hip disease. The status of the articular cartilage at the time of surgery is the most important predictor of treatment success or failure

Introduction. Uncemented porous coated acetabular components have gained more research emphasis in recent years compared to their cemented counterparts, largely owing to the natural biological fixation they offer. Nevertheless, sufficient peri-prosthetic bone ingrowth is essential for long-term fixation of such uncemented acetabular components. The phenomenon of bone ingrowth can be predicted based on mechanoregulatory principles of primary bone fracture healing. Literature review reveals that the surface texture of implant plays a major role in implant-bone fixation mechanism. A few insilico models based on 2-D microscale finite elements (FE) were reported in literatures to predict the influence of surface texture designs on peri-prosthetic bone ingrowth. However, most of these studies were based on FE models of dental implants. The primary objective of this study, therefore, is to mechanobiologically predict the influence of surface texture on bone- ingrowth in acetabular components considering a novel 3-D mesh-shaped surface texture on the implant. Materials/Methods. The 3-D microscale model [Fig.1] of implant-bone interface was developed using CATIA. ®. V5R20 software (DassaultSystèmes, France) and was modelled in ANSYS V15.0 FE software (Ansys Inc., PA, USA) using coupled linear elastic ten-noded tetrahedral finite elements. The model consists of cast-inbeaded mesh textured implant having finely meshed inter-bead spacing. Linear, elastic and isotropic material properties considering Young's modulus of 210 GPa and Poisson's ratio of 0.3 for stainless steel implant were employed in the model. Boundary of bone was assumed to be rich in Mesenchymal Stem Cells(MSC) with periodic boundary conditions at contralateral surfaces. The linear elastic material properties in the model were updated iteratively through a tissue differentiation algorithm that works on the principle of mechanotransduction driven by local mechanical stimuli, e.g. hydrostatic pressure and equivalent deviatoric strain. Results. Results indicate that bone ingrowth is inhibited upon increasing the inter-bead spacing and upon decreasing the bead aspect ratio. It has been observed that there is a predominant influence of bead spacing diameter on the peri-acetabular bone ingrowth. The increase in bead spacing diameter has led to increased bead height that is found to promote higher bone ingrowth with an increase in average Young's modulus of neo-tissue layer. Conclusions. The present study focussed on the development of a new texture on the implant surface and to study the influence of surface texture on bone-ingrowth in acetabular components. Since there is a promising increase in average Young's modulus of the newly formed tissue layer, it predicts the increase in stiffness of the newly formed tissue. The increase in tissue stiffness reveals that, there is not much inhibition in bone ingrowth after the employment of the acetabular implant. The numerical study based on mechanoregulatory algorithm considering the appropriate mechanical stimuli responsible for bone ingrowth, reveals that, compared to hemispherical beaded surface texture, mesh shaped surface texture provides an improved fixation of the acetabular component. For any figures or tables, please contact the authors directly

Purpose. To validate a small, easy to use and cost-effective augmented marker-based hybrid navigation system for peri-acetabular osteotomy [PAO] surgery. Methods. A cadaver study including 3 pelvises (6 hip joints) undergoing navigated PAO was performed. Inclination and anteversion of two navigation systems for PAO were compared during acetabular reorientation. The hybrid system consists of a tracking unit which is placed on the patient's pelvis and an augmented marker which is attached to the patient's acetabular fragment. The tracking unit sends a video stream of the augmented marker to the host computer. Simultaneously, the augmented marker sends orientation output from an integrated inertial measurement unit (IMU) to the host computer. The host computer then computes the pose of the augmented marker and uses it (if visible) to compute acetabular orientation. If the marker is not visible, the output from the IMU is used to update the orientation. The second system served as ground truth and is a previously developed and validated optical tracking-based navigation system. Results. Mean absolute difference for inclination and anteversion (N = 360) was 1.34 degrees and 1.21 degrees, respectively. The measurements from our system show a very strong correlation to the ground-truth optical tracking-based navigation system for both inclination and anteversion (0.9809 / 0.9711). Conclusion. In this work, we successfully demonstrated the feasibility of our system to measure inclination and anteversion during acetabular reorientation

Background. The use of robotics in joint arthroplasty was initiated in 1992 with the introduction of the ROBODOC® Surgical Assistant device for planning and active robotic preparation of the femoral canal in THA. From 1993–1996, an FDA trial was undertaken using pin-based fiduciary markers to register the CT to the robot coordinate system. From 2000–2006, a second FDA trial was initiated using a point-to-surface matching “pinless” registration system. Combined, these two studies offer the first long-term follow-up of robot-assisted THA using an active robotic system for preparation of the femoral canal during THA. Methods. Due to the support of an open implant architecture, patients were implanted with either the Depuy AML, Howmedica Osteoloc, or Zimmer VerSys FMT. Combining patients from the two studies, 86 THA's were performed in 63 patients using the active robotic system. Of these 63 patients, 7 were confirmed to have died and 5 have been lost to follow-up, 2 declined to participate due to infirmity, 37 are still recruiting, and 12 are currently enrolled (16 hips). Data collected included: Harris Hip Scale, HSQ-12, WOMAC, UCLA Activity Score, VAS Pain Score as well as radiographic analysis. The demographics at follow-up were:. Results. There were no revisions of the femoral component for aseptic reasons. Of the 16 hips enrolled, only two have required reoperation for head and liner change. Clinical results are given below:. Radiographic analysis found that peri-acetabular osteolysis was present in 12.5% of hips, AP femoral osteolysis was found in 18.8% of hips, above and lateral femoral osteolysis was found in 6.3% of cases. Conclusions. The use of active robotics for preparation of the femoral canal in THA appears safe and effective at a long-term follow-up of 14 years. The clinical results are comparable to or better than other long term studies of cementless femoral stem prostheses in terms of Harris Hip score (Aldinger et al 2003) and WOMAC Pain, Stiffness, and Physical Function score (Popischill and Knahr 2005). Patient recruitment is still ongoing

Endoprosthetic reconstruction for pathologic acetabular fractures is associated with a high risk of periprosthetic joint infection. In this setting, bone defect reconstruction utilising co-delivery of a synthetic bone substitute with an antibiotic, is an attractive treatment option from both, therapeutic and prophylactic perspective. We wished to address some concerns that remain regarding the possible presence of potentially wear inducing particles in the periprosthetic joint space subsequent to this procedure. We analysed a drain fluid sample from an endoprosthetic reconstruction of a pathologic acetabular fracture with implantation of a gentamicin eluting, biphasic bone graft substitute, consisting of 40% hydroxyapatite (HA) and 60% calcium sulphate (CERAMENT G), into the residual peri-acetabular bone defect. This sample was divided into two 1.5ml subsamples, to one of which 100mg HA particles were added as control before burning off all organic substance at very high temperature. These heat treated samples were then examined with scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDAX) and compared to a reference sample consisting of HA particles only. On SEM, hydroxyapatite particles were readily recognisable in the control and reference samples, whereas only very few particles over 2μm were apparent in the ”pure” drain sample. EDAX revealed that very large amounts of salts were present in both drainage samples. The pure drainage sample however, contained markedly lower amounts of calcium and phosphate compared to reference and control samples. No HA particles as such, were seen in the pure sample, however their presence cannot be excluded with absolute certainty, as some particles might have been hidden within the large salt conglomerates. We could not find clear evidence that the drain fluid really contained HA particles. More thorough investigations are needed and future analyses with prior removal of the high salt content would likely yield more conclusive results

Purpose. The hip region is the second most common site for tuberculosis following the spine in children. The aim is to describe the variable radiological patterns of presentation and their resemblance to pyogenic infection, tumours and other benign conditions of bone in children. Methods. The clinical and radiological records of 29 children aged 10 months–13 years with confirmed tuberculosis of the hip region seen between 1990 and 2011 were reviewed retrospectively. Clinical features were pain, limp and flexion, adduction contractures. Abscesses and sinuses were seen in 4 children. The ESR ranged between 7–110 mm/hr. Mantoux was positive in 20 children. All cases were histologically confirmed. Treatment involved biopsy, currettage of bone defects, limited synovectomy and adductor tenotomy. Patients were immobilised for 4 weeks on a spica cast or traction. Antituberculous treatment was administered for 9–12 months. Results. Radiologically 9 lesions were extra-articular and 20 involved the joint synovium and articular surface. Extra-articular lesions were seen in the pubis, greater and lesser trochanter, ilium, proximal femur and peri-acetabular regions. Intra-articular lesions were seen in the femoral head, neck and acetabulum. Dislocations and subluxations occurred in 8 patients; various lesions mimicked pyogenic arthritis, idiopathic chondrolysis, chondrobastoma, Perthes disease, eosinophilic granuloma and osteoid osteoma. Follow up ranged between 8 months and 5 years. Good range of movement was seen in 20 children. Nine children had flexion adduction contractures, four of these had ankylosed hips and five required abduction extension osteotomies. Other changes seen were coxa vara (2) coxa magna (1) and avascular necrosis (3). Conclusion. The variable radiological picture of tuberculosis of the hip region can mimic various osteoarticular conditions in children. Biopsy is essential and should be taken from the bony lesion and not the synovium alone. NO DISCLOSURES

Introduction. Metal on metal hip bearings (MoM) are under scrutiny. Short and mid-term complications attributed to metal wear debris have been reported. Distinctions between MoM prostheses exist. Thus, generalizing findings from one design to another is questionable. This study reports minimum 5 yr. Pinnacle™ modular MoM results. Methods. Between September 2001 and October 2004, 95 consecutive MoM THAs were performed by one surgeon in a prospective cohort design. Mean age was 53 yrs (range 34-70); 57 were male. Mean BMI was 29 (range 20-46). OA was noted in 87 patients. Head size was 28mm in 3 and 36mm in 92. Surgical approach was postero-lateral in all patients. Harris Hip Score (HHS), WOMAC, ROM and radiographs were evaluated preoperatively, at 6-months, and yearly thereafter. Results. Mean follow-up was 6 yrs (SD 1.7). Mean radiographic follow-up was 5.2 yrs (SD 1.2). Radiographs were available for 83 hips. Mean HHS improved from 43 preoperative (range 15–68) to 98 (range 86-100, p < 0.0001). Mean WOMAC score improved from 56 (range 15-94) to 12 (range 0-63, p < 0.0001). Flexion improved from 95° (range 50-115) to 102° (range 90-120, p < 0.0001). Complications included trochanteric fx (6 mo) without component removal, traumatic femoral Fx (40 days) with stem replacement, and one dislocation. No other device related adverse events were reported. No peri-acetabular osteolysis was observed. Six year survival was 100% for the acetabular shell/modular metal liner combination. Conclusion. Excellent mid-term results were obtained in a young, active cohort treated with modular MoM THA. No AVAL, pseudotumor, unexplained pain or other complication attributable to wear debris or the MoM articulation was observed. These findings indicate that THA with the Pinnacle(tm) modular MoM bearing performs well in a high demand population at mid term follow-up

Limited postoperative range-of-motion (ROM) can lead to patient dissatisfaction and dislocation in total hip arthroplasties (THAs). To avoid this, femur first approaches have been developed which optimise particular aspects of ROM by using a virtual analysis of ROM. This study analysis whether it is possible to accurately assess ROM based on an intra-operative acquisition of anatomical structures by using an image-free navigation system. It compares the outcome of a collision detection algorithm when using 3d models from computerised tomography (CT) scans on the one side and intra-operatively acquired 3D models on the other side within a cadaver study. It focuses on peri-acetabular impingements. During the cadaver session 14 hips (7 cadavers) were treated surgically by using press-fit implants. 3D models of the pelvis and femora were generated based on segmented pre-operative CT data sets. Intra-operative data acquisition was performed by using a CT-free navigation software. Beside standard landmarks, points at the acetabular rim and femoral resection plane were acquired. For assessing ROM, a 3D model of the pelvis was generated. The information about the femoral resection plane was directly entered into the collision detection algorithm. 3D Computer Aided Design (CAD) models provided by the implant manufacturer were used for the implants. Based on this setup, the ROM values for flexion (FLEX), external rotation at 0° flexion (EXT), and internal rotation at 90° flexion (INTROT90) were compared. Differences within intended ROM were considered relevant, since the goal was to enable the prevention of clinically relevant ROM limitations. The average difference between the CT based and navigation data based ROM analysis was 2.13° ± 3.11° for FLEX, 3.33° ± 5.51° for EXT, and 1.6° ± 3.66° INTROT90. The values reduce to 1.58° ± 2.78° (FLEX) and 0.91° ± 3.77° (INTROT90) when only ROM values within the intended ROM are considered. For EXT all ROM values lied above the threshold for intended ROM. Thus, no relevant differences were found for this motion direction. In this study, a real-time collision detection based approach was developed and evaluated, which allows to virtually detect prosthetic and bony impingements. It was shown that ROM can be assessed accurately based on an image-free navigation technique. This information can be used intra-operatively to adjust the position of the implants and thus avoid postoperative ROM limitations. In particular, it enables a comprehensive femur first approach which allows us to optimise the post-operative results regarding functional parameters like ROM

Prior to the 1970s, almost all bone sarcomas were treated by amputation. The first distal femoral resection and reconstruction was performed in 1973 by Dr Kenneth C Francis at the Memorial Sloan-Kettering Cancer Centre in New York. Since that time, limb-sparing surgery for primary sarcoma has become the mainstay of sarcoma surgery throughout the world. Initially, the use of mega-prostheses of increasing complexity, involving all the major long bones and both pelvic and shoulder girdles, was popularised. In the early 1980s, wide use of massive allograft reconstructions became widespread in both Europe and in multiple centres in the USA and UK. Since that time, increasing complexity in the design of prostheses has allowed for increasing functional reconstructions to occur, but the use of allograft has become less popular due to the development of late graft failures of patients survive past ten years. Fracture rates approaching 50% at 10 years are reported, and thus, other forms of reconstruction are being sought. Techniques of leg lengthening, and bone docking procedures to replace segmental bone loss to tumour are now employed, but the use of biological vascularised reconstructions are becoming more common as patient survivorship increases with children surviving their disease. The use of vascularised fibular graft, composite grafts and re-implantation of extra-corporeally irradiated bone segments are becoming more popular. The improvement in survivorship brought about the use of chemotherapy is producing a population of patients with at least a 65% ten year survivorship, and as many of these patients are children, limb salvage procedures have to survive for many decades. The use of growing prostheses for children have been available for some 25 years, first commencing in Stanmore, UK, with mechanical lengthening prostheses. Non-invasive electro-magnetic induction coil mechanisms are now available to produce leg lengthening, with out the need for open surgery. Whilst many of these techniques have great success, the area of soft tissue attachment to metallic prostheses has not been solved, and reattachment of muscles is of great importance, of course, for return of function. There are great problems in the shoulder joints where sacrifice of rotator cuff muscles is necessary in obtaining adequate disease clearance at the time of primary resection, and a stable shoulder construct, with good movement, has yet to emerge. Similar areas of great difficultly remain the peri-acetabular and sacro-iliac resections in the pelvis. Perhaps the real future of the art of limb salvage will be in the reconstruction of failed major joint replacements where there is great loss of bone stock, and already massive tumour prostheses are providing a salvage pathway for failed standard joint replacement. The final future for limb salvage, however, may not rest with increasing surgical complexity and innovation, but with the development of molecular biology and specific targeted treatments, according to the cytogenetics of a particular tumour. We are on the threshold of yet another quantum change in the approach to cancer management; just as chemotherapy brought a tremendous change in the 1970s, molecular biology is the frontier to make much of the current limb salvage surgery that is performed redundant