Purpose. The aim of the study was to assess the efficacy of a cementless acetabular cup without bone grafting in a cohort of patients with protrusio acetabuli who were treated with total hip arthroplasty. Methods. We retrospectively reviewed the records of a cohort of 45 patients with protrusio acetabuli who received elective total hip replacements between 2009 and 2011 at Tygerberg Academic Hospital. We reviewed pre- and post-operative radiographs and the most recent follow-up radiographs (minimum of three months) to assess cup osteointegration. We classified protrusio acetabuli according to Sotelo-Garza and Charnley into mild, moderate and severe, by evaluating pre-operative radiographs. Results. Our cohort of had a median age of 63 years and had a female of male ratio of 4 to 1. The mean follow up was 11 months. We had 9 mild, 29 moderate and 7 severe protrusio cases. At follow-up all cups showed signs of osteointegration with no signs of loosening. Conclusion. The use of a cementless, plasma coated, dual radius acetabular cup without bone grafting in primary THR in protrusio acetabuli provides good primary stability with satisfactory short term radiological outcome. NO DISCLOSURES

Introduction

This study was to investigate the association of developmental dysplasia of the hip (DDH) and primary protrusion acetabuli (PPA) with Vitamin D receptor polymorphisms TaqI and FokI and oestrogen receptor polymorphisms Pvu II and XbaI.

Protrusio acetabuli (arthrokatadysis or Otto pelvis) is a relatively rare condition associated with secondary osteoarthritis of the hip. Radiographically, protrusio acetabuli is present when the medial aspect of the femoral head projects medial to Kohler's (ilioischial) line. This results in medialization of the center of rotation (COR) of the hip. Protrusio acetabuli is typically associated with metabolic bone disease (osteoporosis, osteomalacia, Paget's disease) or inflammatory arthritis (RA or ankylosing spondylitis). Idiopathic acetabular protrusio can occur without the above associated factors however. Patients with protrusio acetabuli typically present with significant restriction of range of motion (ROM) of the hip due to femoral neck and trochanteric impingement in the deep acetabular socket and pain associated with secondary osteoarthritis (OA). Total hip arthroplasty (THA) in patients with protrusion acetabuli is more challenging than THA in patients with a normal hip COR. ROM is typically quite restricted which can compromise surgical exposure. Dislocation of the hip in the patient with a deep socket and medialised COR can be extremely difficult and associated with fracture of the femur if not carefully performed. Restoration of the hip COR to the normal more lateralised position is a principle goal of surgery. This restores more normal mechanics of the hip and has been associated with improved durability. A variety of techniques to accomplish this have been described including medial acetabular bone grafting with cemented cups, protrusio rings or porous coated cementless cups fixed with multiple screws. The latter technique has been shown to be more durable and associated with better outcomes. THA in protrusio acetabuli starts with templating of the preoperative x-rays to determine the optimal acetabular implant size and final position of the acetabular component that restores the hip COR to the normal position. Patients with protrusio acetabuli often have varus oriented femoral necks and the femur needs to be carefully templated as well to insure that an appropriate femoral component is available that will allow for restoration of the patient's anatomy. Cartilage covering the thinned medial wall needs to be carefully removed without disruption of the medial acetabular wall. The acetabulum is then carefully reamed with the goal of obtaining stable peripheral rim support of a cementless socket and at least 50% contact of the implant on good quality host bone. Unlike acetabular preparation in the normal hip, preventing the reamer from “bottoming out” is essential in order to obtain desired rim support and return of the hip COR to the normal lateralised position. When good rim support of the reamer is obtained, a trial component is placed and intraoperative x-ray obtained to confirm fit, position and restoration of hip COR. Limited addition reaming can be performed to obtain desired degree of press fit (1‐2mm) and contact with host bone. Morselised autograft from the femoral head and neck is then packed into the medial defect and reverse reamed. The cementless acetabular component is then impacted into position and fixed with screws. Weight bearing is determined by bone quality, size and containment of the medial defect, amount of contact of the cementless cup with host bone and stability of the acetabular construct. Incorporation of autograft bone in the acetabulum and stable long term fixation occurs reliably if stable initial press-fit fixation of the cementless cup is obtained. Restoration of hip COR to within 7mm of its normal location is associated with better implant survival

Not all total hip arthroplasty cases are created equal is a maxim that holds true for both primary and revision scenarios. Complex cases involve patients presenting with compromised bone and/or soft tissue. For primary cases, these include hips with dysplasia, ankylosis, deformed proximal femora, protrusio acetabuli, prior hip fracture with or without failed fixation, previous bony procedures, or neuromuscular conditions. In revision surgery, complex scenarios include cases compromised by bone loss, deterioration of the soft tissues and resulting in dislocation and instability, peri-prosthetic fracture, leg length discrepancy, infection, and more recently, hypersensitivity reactions. Meticulous surgical technique including component placement is essential. In this interactive session, a moderator and team of experts will discuss strategies for evaluation and management of a variety of challenging hip case scenarios

Protrusio acetabuli can be either primary or secondary. Primary or idiopathic protrusio is a rare condition of unknown etiology. Secondary protrusio may be associated with rheumatoid arthritis, ankylosing spondylitis, osteoarthritis, osteomalacia, trauma and Paget's disease. Challenges in surgery include: lack of bone stock, deficient medial support to the cup, difficulty in dislocating the femoral head, and medialization of the hip joint center. Several surgical techniques have been described: use of cement alone without bone graft; morselised impacted autograft or allograft with a cemented cup; metal cages, reinforcement rings, and solid grafts. We describe our technique of impaction grafting using autologous bone and a cementless porous-coated hemispherical cup without the use of acetabular rings or cages in patients with an average age of 46 years. Protrusion was graded depending on distance of medial wall from Kohler's line as mild (1–5 mm medial), moderate (6–15 mm medial) and severe if it was more than 15 mm medial to the Kohler's line. All patients were operated in the lateral position using a modified Hardinge's anterolateral approach. Adductor tenotomy may be required in cases of severely stiff hips. After careful dislocation of the femoral head, it was sectioned in situ into slivers to facilitate obtaining the graft. The periphery was reamed and care was taken to preserve the membrane lining the floor of the defect. Morselised graft was impacted with hemispherical impactors and the trial cup 1–2 mm larger than the last reamer placed in the desired position. The final socket was then inserted. Femoral preparation was performed in routine fashion. The mean pre-operative Harris Hip Score of 52 improved to 85 points at a mean follow up of 4 years. The average acetabular inclination angle was 42 degrees. Our results have shown incorporation of the graft in all cases. There was no evidence of progression of the protrusio or cup loosening in any of the cases. Thus far, our hips have not shown osteolytic lesions. The technique described is a satisfactory biological solution of restoring bone stock particularly in young and middle-aged patients

Not all total hip arthroplasty cases are created equal is a maxim that holds true for both primary and revision scenarios. Complex cases involve patients presenting with compromised bone and/or soft tissue. For primary cases, these include hips with dysplasia, ankylosis, deformed proximal femora, protrusio acetabuli, prior hip fracture with or without failed fixation, previous bony procedures, or neuromuscular conditions. In revision surgery, complex scenarios include cases compromised by bone loss, deterioration of the soft tissues and resulting instability, periprosthetic fracture, leg length discrepancy, infection, and more recently, hypersensitivity reactions. In this interactive session, a moderator and team of experts will discuss strategies for evaluation and management of a variety of challenging hip case scenarios

Not all total hip arthroplasty cases are created equal is a maxim that holds true for both primary and revision scenarios. Complex cases involve patients presenting with compromised bone and/or soft tissue. For primary cases, these include hips with dysplasia, ankylosis, deformed proximal femora, protrusio acetabuli, prior hip fracture with or without failed fixation, previous bony procedures, or neuromuscular conditions. In revision surgery, complex scenarios include cases compromised by bone loss, deterioration of the soft tissues and resulting instability, periprosthetic fracture, leg length discrepancy, infection, and more recently, hypersensitivity reactions. In this interactive session, a moderator and team of experts will discuss strategies for evaluation and management of a variety of challenging hip case scenarios

Introduction. Computer navigation systems are quite sophisticated intra-operative support systems for the precise placement of acetabular or femoral components in THA. However, few studies have addressed the clinical benefits derived from using a navigation system to achieve precise placement of the implants. The purpose of this study is to investigate the early dislocation rate of navigation-assisted primary THA through a posterior approach in order to clarify the short-term benefit of using a computer navigation system. Methods. We retrospectively reviewed the early dislocation rate (within 12 months after surgery) of 475 consecutive primary cementless or hybrid THAs with femoral head sizes ≦32mm performed via posterior approach. There were 85 men and 390 women, with a mean age of 60 years (17 to 88) at operation. Preoperative diagnoses included osteoarthritis in 384 hips, osteonecrosis in 45 hips, and others in 46 hips (ex. RA, trauma, infection, congenital disease). All THAs were planned using a 3D templating system based on the combined anteversion theory, performed by single surgeon through a posterior approach with repair of the posterior capsule, assisted by a CT-based surface matching type computer navigation system for cup implantation. All patients were directly followed up at least 1 year after surgery. We classified all 475 joints into four groups: normal or mildly deformed hips (Group A; 308 joints, ex. primary OA, Crowe group 1, osteonecrosis), moderately deformed hips (Group B; 97 joints, ex. Crowe group 2, protrusio acetabuli, Perthes like deformity), severely deformed hips (Group C; 53 joints, ex. Crowe group 3 or 4, ankylosis, fused hip), and neuromuscular and cognitive disorders (Group D; 17 joints), and examined the dislocation rate for each group. Results. We had eleven early dislocations, for an overall dislocation rate of 2.3% (11/475). All dislocations occurred posteriorly within 6 weeks after surgery. Three joints were Crowe group 4 dislocated hips, three were Charcot joints, two were Girdlestone hips after pyogenic arthritis, two was a Crowe group 1 hip, and one was osteonecrosis. All 11 cups were implanted within 5 degree of error from the preoperative planning, and all were placed within the Lewinnek safe zone. The dislocation rates according to group were 0.6% for group A (2/308), 0% for B (0/97), 9.4% for C (5/53), and 23.5% for D (4/17). Discussion. The use of computer navigation system in patients undergoing THA improves the precision of acetabular cup placement by decreasing the number of outliers, which may result in reducing the risk of dislocation. In this series, most dislocations occurred in the highly risky or rare condition cases in groups C or D. In such cases, precise and appropriate cup implantation assisted by the navigation system could not completely prevent dislocation because of the patients' specific special backgrounds. On the other hand, early dislocation was prevented for the normal/mild to moderately deformed joints such as those in groups A or B. Computer navigation system was effective for prevent early dislocation in the normal or mild to moderately deformed joints

Protrusio acetabuli can be either primary or secondary. Primary or idiopathic protrusio is a rare condition of unknown etiology. Secondary protrusio may be associated with rheumatoid arthritis, ankylosing spondylitis, osteoarthritis, osteomalacia, trauma and Paget's disease. Challenges in surgery include lack of bone stock, deficient medial support to the cup, difficulty in dislocating the femoral head, and medialisation of the hip joint center. Several surgical techniques have been described: use of cement alone without bone graft; morsellised impacted autograft or allograft with a cemented cup; metal cages, reinforcement rings, and solid grafts. We describe our technique of impaction grafting using autologous bone and a cementless porous-coated hemispherical cup without the use of acetabular rings or cages in patients with an average age of 46 years. Protrusion was graded depending on distance of medial wall from Kohler's line as mild (1–5mm medial), moderate (6–15mm medial) and severe if it was more than 15mm medial to the Kohler's line. All patients were operated in the lateral position using a modified Hardinge's anterolateral approach. Adductor tenotomy may be required in cases of severely stiff hips. After careful dislocation of the femoral head, it was sectioned in situ into slivers to facilitate obtaining the graft. The periphery was reamed and care was taken to preserve the membrane lining the floor of the defect. Morsellised graft was impacted with hemispherical impactors and the trial cup 1–2mm larger than the last reamer placed in the desired position. The final socket was then inserted. Femoral preparation was performed in routine fashion. The mean preoperative Harris hip score of 52 improved to 85 points at a mean follow up of 4 years. The average acetabular inclination angle was 42 degrees. Our results have shown incorporation of the graft in all cases. There was no evidence of progression of the protrusio or cup loosening in any of the cases. Thus far, our hips have not shown osteolytic lesions. The technique described is a satisfactory biological solution of restoring bone stock particularly in young and middle-aged patients

Protrusio acetabuli can be either primary or secondary. Primary or idiopathic protrusio is a rare condition of unknown etiology. Secondary protrusio may be associated with Rheumatoid Arthritis, Ankylosing spondylitis, osteoarthritis, osteomalacia, trauma and Paget's disease. Challenges in surgery include lack of bone stock, deficient medial support to the cup, difficulty in dislocating the femoral head, and medialisation of the hip joint centre. Several surgical techniques have been described: use of cement alone without bone graft; morsellised impacted autograft or allograft with a cemented cup; metal cages, reinforcement rings, and solid grafts. We describe our technique of impaction grafting using autologous bone and a cementless porous-coated hemispherical cup without the use of acetabular rings or cages in patients with an average age of 46 years. Protrusion was graded depending on distance of medial wall from Kohler's line as mild (1–5 mm medial), moderate (6–15 mm medial) and severe if it was more than 15 mm medial to the Kohler's line. All patients were operated in the lateral position using a modified Hardinge's anterolateral approach. Adductor tenotomy may be required in cases of severely stiff hips. After careful dislocation of the femoral head, it was sectioned in situ into slivers to facilitate obtaining the graft. The periphery was reamed and care was taken to preserve the membrane lining the floor of the defect. Morsellised graft was impacted with hemispherical impactors and the trial cup 1–2 mm larger than the last reamer placed in the desired position. The final socket was then inserted. Femoral preparation was performed in routine fashion. The mean pre-operative Harris hip score of 52 improved to 85 points at a mean follow up of 4 years. The average acetabular inclination angle was 42 degrees. Our results have shown incorporation of the graft in all cases. There was no evidence of progression of the protrusio or cup loosening in any of the cases. Thus far, our hips have not shown osteolytic lesions. The technique described is a satisfactory biological solution of restoring bone stock particularly in young and middle-aged patients

The contemporary practice of orthopaedic surgery requires an evidence-based approach to support all medical and surgical interventions. In this essay, the author expresses a forthright, personal and somewhat prejudiced appeal to retain the legitimacy of clinical decision making in conditions that are rare, contain multiple variables, have a solution that generally works or has an unpredictable course.

Cite this article: Bone Joint J 2014;96-B:1002–4.