Introduction. Pedicle subtraction osteotomy is a powerful technique for correcting sagittal imbalance in ankylosing spondylitis. There has been significant perioperative morbidity associated with this technique in the peer review literature. We present the Royal National Orthopaedic Hospital experience with a single surgeon retrospective study that was conducted to evaluate the outcomes in patients who underwent lumbar pedicle subtraction osteotomy for the correction of thoracolumbar kyphotic deformity in ankylosing spondylitis. Method. Twenty seven patients underwent a lumbar pedicle subtraction osteotomy and adjacent level posterior instrumentation between 1995 and 2010. There were 18 males and 9 females in the study. Events during the peri-operative course and post-operative complications were recorded. The radiological outcome and patient satisfaction were analysed with mean follow-up of one and a half years. Results. The mean operative time was three and half hours and the mean blood loss was 2290mls. Final follow-up radiograph showed an increase in lumbar lordosis angle from 17 degrees to 45 degrees. The sagittal imbalance improved by 85mm with the operation. Complications included loosening in two patients, one transient neurologic deficit and one infective non-union occurred overall. There were no mortalities from the surgery. Two patients developed junctional kyphosis and required a repeat operation. There was an improvement in the Oswestry Disability Score from a mean of 29 to 16 after the surgey. All (100%) of the patients were satisfied with the results of the procedure and would recommend the surgey to others. Conclusion. The study shows that pedicle subtraction extension osteotomy is effective for the correction of kyphotic deformity in ankylosing spondylitis

We retrospectively reviewed 54 patients (92 hips) who underwent cementless total hip arthroplasty for bony ankylosis in ankylosing spondylitis between September 1988 and 2002. Clinical assessment was done at follow-up, which envisages assessment of the pain, function, deformities and range of motion using the Harris Hip Score. Radiographic analysis was done. Kaplan-Meier survivorship analysis was done at 5 and 8.5 years using the revision for the removal of femoral component, acetabular component or both due to any cause as the end point. The mean age of the patients was 25.5 years. The mean duration of follow up was 8.5 years. The average preoperative Harris Hip Score of 49.5 improved to 82.6 post operatively. Post operatively 10 hips had mild to moderate pain. Anterior dislocation occurred in four hips (4.3 %) and sciatic nerve palsy in one hip. Heterotopic ossification was seen in 12 patients, reankylosis rate was 0%. Thirteen arthroplasties were revised due to aseptic loosening. Kaplan-Meier survivorship analysis with revision as end point revealed 98.8% survival at 5 years and 85.8% survival at 8.5 years 11 follow up. Cementless THA in osseous ankylosis in ankylosing spondylitis is a worthwhile surgical intervention in bony ankylosis. Newfound mobility, manoeuvrability and improved ability to sit comfortably were the outcomes, which alleviated the patients’ daunted morale. However, the technically demanding nature of the procedure should not be underestimated

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

Background. Heterotopic ossification (HO) is a known complication following total hip arthroplasty, with increased incidence in certain patient populations. Current prophylaxis options include oral non-steroidal anti-inflammatory drugs (NSAIDs) and radiation therapy, but an optimal radiation protocol has yet to be clearly defined. We performed a randomized, double-blinded clinical trial in high-risk total hip arthroplasty patients to determine the efficacy of 400 cGy versus 700 cGy doses of radiation. Methods. 147 patients at high risk for HO undergoing total hip arthroplasty (THA) at Rush-St. Luke's- Presbyterian medical center were randomized to either a single 400 cGy or 700 cGy dose of radiation. High risk was defined as diagnosis of diffuse idiopathic skeletal hyperostosis (DISH), hypertrophic osteoarthritis, ankylosing spondylitis, or history of previous heterotopic ossification. Radiation was administered over a 14 × 6 cm area of soft tissue and given on the first or second post-operative day. A blinded reviewer graded anterior-posterior (AP) and lateral radiographs taken immediately post-operatively and at a minimum of 6 months post-operatively. Progression was defined as an increase in Brooker classification from the immediate post-operative to the long-term post-operative radiograph. Operative data including surgical approach, use of cemented implants, revision surgery, and post-operative range of motion data were also collected. Results. A significantly greater portion of patients who received the 400 cGy dose demonstrated progression of HO than patients who received the 700 cGy dose. No pre-operative factors were associated with a higher rate of progression. Patients who progressed had less flexion on physical exam than patients who did not progress, but this was not clinically significant. Conclusion. To the authors' knowledge this is the largest randomized prospective study to date comparing two single-dosages of radiation treatment. 700 cGy demonstrates superiority over 400 cGy in preventing HO formation following total hip arthroplasty in high-risk patients and may be the more effective treatment in this population

Introduction. The purpose of this retrospective study was to review the outcome of THA in the treatment of bilateral hip ankylosis of different causes; surgical, septic or spontaneous. Methods & Material. 20 THA procedures in 10 patients were included in the study, 5 males and 5 females all had bilateral fusion. Previous pathologies included: ankylosing spondylitis, AVN, septic arthritis and surgical arthrodesis. Flexion deformity ranged (10°-45°). Shortening as compared to normal anatomy was up to 6 cm and leg length discrepancy (LLD) ranged from 1 cm to 2.5 cm. Most unified X-ray finding was massive osteophytes formation with 3 patients showing severe narrowing of the femoral canal. Operative time averaged 147 minutes (70–210) and lateral approach was used in all patients, anesthesia was general with only 3 undergoing spinal anesthesia. Results. Serious complications were reported and were related to the correction of LLD; 1 incidence of sciatic nerve injury that recovered in one year, and another incidence of femoral nerve injury (sensory > motor) that recovered within 3 months, and one case of incomplete correction of LLD. At 5 years follow up (minimum 6 month), there is no loosening or revision. Discussion. The conversion of bilateral fused hip joints to THA is a very rewarding surgery but with higher risk of complications

Hip resurfacing offers an attractive alternative to conventional total hip arthroplasty in young active patients. It is particularly advantageous for bone preservation for future revisions. Articular Surface Replacement (ASR) is a hip resurfacing prosthesis manufactured by DePuy Orthopaedics Inc. (Warsaw, IN). The manufacturer voluntarily recalled the ASR system in 2010 after an increasing number of product failures. The present study aimed to determine the long-term results in a large cohort of patients who received the ASR prosthesis. Between February 2004 and August 2010, 592 consecutive hip resurfacings using the ASR (DePuy Orthopaedics Inc., Warsaw, IN) resurfacing implant were performed in 496 patients (391 males and 105 females). The mean age of the patients at the time of the surgery was 54 (range: 25 to 74) years. Osteoarthritis was the most common diagnosis in 575 hips (97.1%). The remaining patients (2.9%) developed secondary degenerative disease from ankylosing spondylitis, avascular necrosis, developmental hip dysplasia, and rheumatoid arthritis. Clinical and radiographic information was available for all patients at the last follow up. Cobalt (Co) and chromium (Cr) levels were measured in 265 patients (298 hips) by inductively coupled plasma-mass spectrometry (ICP-MS). The average follow up of the study was 8.6 years (range: 5.2 to 11.6 years). The mean Harris hip and UCLA scores significantly improved from 44 and 2 pre-operatively to 85.3 and 7.1 respectively. The median Co and Cr ion level was 3.81 microgram per liter and 2.15 microgram per liter respectively. Twenty-seven patients (5.4%) were found to have blood levels of both Co and Cr ions that were greater than 7 microgram per liter. Fifty-four patients (9.1%) were revised to a total hip arthroplasty. Kaplan-Meier survival analysis showed a survival rate of 87.1% at 8.6 years with revision for any cause and 87.9% if infection is removed. A significantly higher survival rate was observed for the male patients (90.2%, p <0.0001) and for the patients with ASRs with femoral heads diameters larger than 52 mm (90.1%, p=0.0003). This study confirms that patient selection criteria are of great importance to the overall survivorship of hip resurfacing arthroplasty. Improved clinical results have been reconfirmed with the use of larger diameter femoral heads

Introduction. Total hip arthroplasty (THA) is becoming a common procedure because it dramatically relieves the patient's pain. Accordingly, young patients who hope to take THAs are also increasing. The results of THAs in the young patients have historically shown relatively poor survivorship. However several improvements of components may promise good long term results in active young patients. There was no consensus about the appropriate time for performing THA. The purpose of this study is to review the results of THAs younger than 40 years. Material and methods. A retrospective review of 14 primary THAs in 12 patients was conducted. The mean age was 27.0 (range 17–30). Ten were female (83%) and 2 were male (17%). The average follow –up period was 38.3 months (range 18–64). All operations were performed using direct anterior approach (DAA). All patients were allowed full weight bearing as tolerated in the immediate postoperative periods. All were cementless THA and the articulation bearing were ceramic/ceramic in 5 hips (33.3%), metal/highly cross linked polyethylene in 8 hips (53.3%), and ceramic/ highly cross linked polyethylene in 2 hips (13.3%). All patients were followed clinically and radiographically. Patients were evaluated at 4,6,12 weeks and each year postoperatively. Patients were allowed sports at 3 months postoperatively without limitations. Results. The underlying etiology was steroid-induced osteonecrosis in 5 patients, alcohol-induced osteonecrosis in 2 patients, developmental dysplasia in 2 patients (1 post osteotomy and 2 conservative therapy), infection in 1 patients, ankylosing spondylitis in 1 patients, and epiphyseal dysplasia in 1 patients. All patients failed conservative treatment. Two patients had prior osteotomy surgeries. Preoperative average JOA score, which is 100 points in full score, was 45 points. Those scores improved to 99 points post operatively. All patients became to walk without any assistive devices. There were no infections and dislocations. Their radiographs showed no loosening, subsidence, and osteolysis. All of their radiographs showed well fixed osseous integrations. Discussion and conclusion. Although our patients were very small numbers and follow up periods were not long, all of our patients showed good clinical and radiological results. When conservative treatments failed to relieve their pain, surgical treatments are required to restore their highly active lives. The modern THA has been showed numerous good results in older generations. With modern implants and surgical technique, we can also expect promising results in young patients under the condition with careful and long term follow-up

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

The aim of the study was to highlight the absence of an important pitfall in the Advanced Trauma Life Support protocol in application of rigid collar to patients with potentially unstable cervical spine injury. We present a case series of two patients with ankylosed cervical spines who developed neurological complications following application of rigid collar for cervical spine injuries as per the ATLS protocol. This has been followed up with a survey of A&E and T&O doctors who regularly apply cervical collars for suspected unstable cervical spine injuries. The survey was conducted telephonically using a standard questionnaire. 75 doctors completed the questionnaire. A&E doctors = 42, T&O = 33. Junior grade = 38, middle grade = 37. Trauma management frontline experience >1yr = 50, <1yr = 25. Of the 75 respondents 68/75 (90.6%) would follow the ATLS protocol in applying rigid collar in potentially unstable cervical spine injuries. 58/75 (77.3%) would clinically assess the patient prior to applying collar. Only 43/75 (57.3%) thought the patients relevant past medical history would influence collar application. Respondents were asked whether they were aware of any pitfalls to rigid collar application in suspected neck injuries. 34/75 (45.3%) stated that they were NOT aware of pitfalls. The lack of awareness was even higher 17/25 (68%) amongst doctors with less that 12 months frontline experience. When directly asked whether ankylosing spondylitis should be regarded as a pitfall then only 43/75 (57.3%) answered in the affirmative. We would like to emphasise the disastrous consequences of applying a rigid collar in patients with ankylosed cervical spine. The survey demonstrates the lack of awareness (∼ 50%) amongst A&E and T&O doctors regarding pitfalls to collar application. We recommend the ATLS manual highlight a pitfall for application of rigid collars in patients with ankylosed spines and suspected cervical spine injuries

Purpose. This study was undertaken to assess the result of total hip arthroplasty (THA) performed for fused hips. Patients and Methods. Twenty nine patients (31 hips), aged 21 to 70 years (average 46 years), underwent THA conversion surgery and were followed for an average of 4.6 years (2.4-12.0 years). There were 23 cases of spontaneous fusion and 8 case of surgical fusion. The causes of joint fusion were tuberculosis in 6 hips, childhood coxitis in 13, ankylosing spondylitis in 6 and childhood trauma in 4. Modified two incision technique was used in 9 hips and in 22 hips, the surgery was performed through a posterolateral approach combined with anterior capsulotomy through gluteus medius and tensor fasica lata interval. In 1 case, greater trochanter osteotomy was done. All acetabular components were inserted at the true acetabulum and the articulations were metal on metal in 7 cases and ceramic on ceramic in 24 cases. Postoperatively, range of motion exercises were encouraged after 2 to 3 weeks of bed rest and subsequent weight bearing crutch ambulation. Then active exercises were strongly encouraged to stretch abductors. We evaluated the clinical and radiological results. Results. Mean duration of surgery was 178.6 minutes, and mean perioperative blood loss was 1420.1 ml. Post-operative dislocation occurred in 1 case and partial femoral nerve palsy developed in 1 case. Mean Harris Hip Score improved from 42.4 to 84.2 and mean leg lengthening of 36.6 mm was achieved. Sitting cross legged was possible in 15 patients and except 2 patients, all patients were satisfied with the surgery. On the radiologic evaluation, there was no changes in cup position and there was one case with acetabular focal osteolysis. Postoperative dislocation occurred in one case and there was no revision surgery or infection. Conclusion. Our study suggest that THA performed for fused hips with hard bearing articulation can provide good clinical and radiological results in mid-term follow up

To consider bilateral simultaneous knee replacement, both knees must have significant structural damage. It is best if the patient can't decide which knee is more bothersome. In borderline cases, ask the patient to pretend that the worse knee is normal and if so, would they be seeing you for consideration of knee replacement on the less involved side. If the answer to this question is “yes,” consider the patient a potential candidate for bilateral knee replacement. If the answer is “no,” recommend operating only on the worse knee, and expect that the operation on the second knee can probably be delayed for a considerable period of time. Strong indications for bilateral simultaneous TKA are bilateral severe angular deformity, bilateral severe flexion contracture, and anesthesia difficulties, i.e., patients who are anatomically or medically difficult to anesthetise, such as some adult or juvenile rheumatoid arthritis patients or patients with severe ankylosing spondylitis. Relative indications for bilateral simultaneous TKA include the need for multiple additional surgical procedures to achieve satisfactory function and financial or social considerations for the patient. Contraindications to bilateral TKA include medical infirmity (especially cardiac), a reluctant patient, and a patient with a very low pain threshold. When performing bilateral simultaneous TKA, both limbs are prepped and draped at the same time. An initial dose of an intravenous antibiotic is given (usually 1g of a cephalosporin) before inflation of the tourniquet. Surgery begins on the more symptomatic side or on either side if neither knee is significantly worse than the other. The reason for starting on the more symptomatic side is in case surgery has to be discontinued after only one procedure owing to anesthetic considerations. After the components have been implanted on the first side, the tourniquet is deflated and a second dose of intravenous antibiotic is administered (usually 500mg of a cephalosporin). After the joint capsule is closed and flexion against gravity is measured, one team completes the subcutaneous and skin closure on the first side while the other team inflates the second tourniquet and begins the exposure of the second side. When the second tourniquet is deflated, a third dose of antibiotic is given (usually 500mg of a cephalosporin for a total dose of 2g for both knees). Because of concern about the potential for cross-contamination of the knee wounds when instruments used during the final stages of skin closure on the first knee are maintained on the field and used on the second knee, they should probably be handed off the field and outer surgical gloves changed. Most patients will report after their complete recovery that they are glad they did both knees at the same time. A patient who has any uncertainty about proceeding with bilateral surgery should have only one knee done at a time. In many cases, the second side receives a “reprieve,” becoming more tolerable after the first side has been operated on

Background. We have performed total knee arthroplasties for valgus and varus in the knees of one person and investigate the clinical characteristics of these patients and the relationship between the kind of deformity and postoperative result. Methods. From March 2002 to February 2010, 25 patients who had simultaneous varus and valgus knee deformities underwent total knee arthroplasties and followed more than 12 months were included. The average age was 66.9 years and the average follow-up period was 61.1 months. Follow-up imaging assessments were taken and clinical outcome were evaluated using HSS score at last follow-up. Results. 11 cases had more pain in varus knee and 8 cases had more pain in valgus knee preoperatively. In 11 cases, degenerative scoliosis were associated with the knee deformity and among the cases, 10 cases had valgus deformities in concave side of scoliosis. In three cases, hip deformities were noted in ipsilateral side of the valgus deformity. One case showed both hip deformities with ankylosing spondylitis. Preoperative mean valgus angle was 11.4 degree and varus angle was 7.5 degree. Postoperative valgus and varus angle improved to 6.3 and −5.7 degree. HSS score improved from 64.3 to 84.7 point in valgus deformities and from 62.1 to 85.1 point in varus deformities. Postoperative patellar clunk syndrome was identified in one valgus knee, but resolved by arthroscopic debridement. And postoperatively, one case showed out-toeing gait caused by equinovarus deformity in varus knee, but resolved by correction of foot deformity. Conclusions. Simultaneous or staged total knee arthroplasties in patients with simultaneous varus with contralateral valgus knee deformities brought satisfactory outcomes with regard to objective orthopedic criteria such as radiographic and clinical results. Concave aspect of scoliosis and hip deformity correlate with valgus knee in statistically. But rheumatoid factor and VDRL do not correlate with valgus deformity. And we found no significant difference between the kind of deformity and postoperative result

Purpose. To evaluate the radiological changes after metal on metal resurfacing arthroplasty. Materials and Methods. Between December 1998 and August 2004, 166 hips in 150 patients who underwent metal resurfacing arthroplasty and followed up more than 4 years. Their mean age at the time of operation was 37.3 years(range, 15–68 years) and mean period of follow-up was 6.1 years(range, 48–95 months). The cause of arthroplasty included 115 avascular necrosis, 43 osteoarthritis, 7 ankylosing spondylitis, 1 haemophilic arthropathy. All patients had anteroposterior, translateral radiographs of the hip made preoperatively and each follow-up visit, and we analyzed radiographic findings such as radiolucencies or impingement signs around implant, neck narrowing and heterotopic ossification. Results. There was a no significant difference between preoperative and postoperative Harris hip score and range of motion. The mean stem-shaft angle was 137.4°, and 55.4% were ranged 130° to 140°. The mean inclination of acetabular component was 44.9°. There were no radiolucent lines or osteolytic lesion around the acetabular components, but 3 hips showed radiolucency around the head-neck junction(1.8%) and 4 hips showed radiolucent line around the stem (2.4%). 12 hips had impingement signs around the head-neck junction (7.2%), and 2 cases showed neck narrowing (1.2%). 3 cases had some heterotopic ossification (1.8%). In 12 cases with impingement signs, the stem-shaft angle and inclination of acetabular component were lower than control group. Pseudotumor was not found in this cohort. Conclusions. This study demonstrates no serious radiological problems till the midterm follow-up after resurfacing arthroplasty, but osteolytic lesion such as radiolucent line around head-neck junction, neck narrowing can be a potential cause of failure in future. Even though the radiolucent line around stem of femoral component revealed no subjective symptom yet, it suggests the micromotion of femoral component which can lead to femoral component loosening. The most common radiological findings, impingement signs, seem not to have clinical significance

To consider bilateral simultaneous knee replacement, both knees must have significant structural damage. It is best if the patient can't decide which knee is more bothersome. In borderline cases, ask the patient to pretend that the worse knee is normal and if so, would they be seeing you for consideration of knee replacement on the less involved side. If the answer to this question is “yes,” consider the patient a potential candidate for bilateral knee replacement. If the answer is “no,” recommend operating only on the worse knee, and expect that the operation on the second knee can probably be delayed for a considerable period of time. Strong indications for bilateral simultaneous TKA are bilateral severe angular deformity, bilateral severe flexion contracture, and anesthesia difficulties, i.e., patients who are anatomically or medically difficult to anesthetise, such as some adult or juvenile rheumatoid arthritis patients or patients with severe ankylosing spondylitis. Relative indications for bilateral simultaneous TKA include the need for multiple additional surgical procedures to achieve satisfactory function and financial or social considerations for the patient. Contraindications to bilateral TKA include medical infirmity (especially cardiac), a reluctant patient, and a patient with a very low pain threshold. When performing bilateral simultaneous TKA, both limbs are prepped and draped at the same time. An initial dose of an intravenous antibiotic is given (usually 1 gram of a cephalosporin) before inflation of the tourniquet. Surgery begins on the more symptomatic side or on either side if neither knee is significantly worse than the other. The reason for starting on the more symptomatic side is in case surgery has to be discontinued after only one procedure owing to anesthetic considerations. After the components have been implanted on the first side, the tourniquet is deflated and a second dose of intravenous antibiotic is administered (usually 500 mg of a cephalosporin). After the joint capsule is closed and flexion against gravity is measured, one team completes the subcutaneous and skin closure on the first side while the other team inflates the second tourniquet and begins the exposure of the second side. When the second tourniquet is deflated, a third dose of antibiotic is given (usually 500 mg of a cephalosporin for a total dose of 2 g for both knees). Because of concern about the potential for cross-contamination of the knee wounds when instruments used during the final stages of skin closure on the first knee are maintained on the field and used on the second knee, they should probably be handed off the field and outer surgical gloves changed. Most patients will report after their complete recovery that they are glad they did both knees at the same time. A patient who has any uncertainty about proceeding with bilateral surgery should have only one knee done at a time. In many cases, the second side receives a “reprieve,” becoming more tolerable after the first side has been operated on

The most frequent cause of failure after total hip replacement in all reported arthroplasty registries is peri-prosthetic osteolysis. Osteolysis is an active biological process initiated in response to wear debris. The eventual response to this process is the activation of macrophages and loss of bone.

Activation of macrophages initiates a complex biological cascade resulting in the final common pathway of an increase in osteolytic activity. The biological initiators, mechanisms for and regulation of this process are beginning to be understood. This article explores current concepts in the causes of, and underlying biological mechanism resulting in peri-prosthetic osteolysis, reviewing the current basic science and clinical literature surrounding the topic.