Introduction. The management of periprosthetic pelvic bone loss is a challenging problem in hip revision surgery. This study evaluates the minimum 10-year clinical and radiographic outcome of major column structural allografts combined with the Burch-Schneider antiprotrusio cage for acetabular reconstruction. Methods. From January 1992 to August 2005, 106 hips with periprosthetic osteolysis underwent acetabular revision using massive allografts and the Burch-Schneider antiprotrusio cage. Forty-five patients (49 hips) died for unrelated causes without further surgery. Fifty-nine hips in 59 patients underwent clinical and radiographic evaluation at an average follow-up of 15.1 years. There were 17 male and 42 female patients, with age ranging from 29 to 83 years (mean 59). Results. Ten hips required rerevision because of infection (3), aseptic loosening (6), and flange breakage (1). Moreover, 4 cages showed x-ray signs of instability with severe bone resorption. The survivorship of the Burch-Schneider cage at 21.9 years with removal for any reason or radiographic migration and aseptic or radiographic failure as the end points were 76.3 and 81.4, respectively. The average Harris hip score improved from 33.2 points preoperatively to 75.7 points at the latest follow-up (p < 0.001). Discussion. In hip revision surgery, severe deficiency of pelvic bone stock is a critical concern because of the difficulty in providing a stable and durable fixation of the prosthesis. Although antiprotrusio cages have a limited role in acetabular revision, the use in association with massive allografts in extended bone loss demonstrated highly successful long-term results, enabling bone stock restoration and cup stability

In North America, and for the most part globally, a cementless acetabular component with adjuvant screw fixation is the preferred technique for revision total hip arthroplasty. However, there are situations that involve massive pelvic bone loss that preclude the use of a cementless cup alone. Options include: . i). Enhanced fixation components and augments. ii). Specialised constructs (cup/cage). iii). Structural allografts. iv). Bone graft substitutes. Complex acetabular revisions present the arthroplasty surgeon with challenges that require an approach with more than one solution for all scenarios. While structural allografts have recently fallen out of favour with the increasing use of enhanced fixation components, there would still appear to be a role in the case in which bone stock restoration is a primary goal. The role of bone graft substitutes remains unclear, with supportive basic science data, but limited clinical experience to date. An algorithm will be discussed to assist in prioritising the multiple goals of acetabular reconstruction and one stock restoration

Goals of femoral revision arthroplasty are to achieve stability of the femoral component, to restore biomechanical function of the hip joint and to restore the femoral bone stock. In order to accomplish such an ideal revision arthroplasty, several points should be reminded before and during the revision arthroplasty such as exposure, removal of the failed component, restoration of bone loss, placement of the new component and hip stability. Appropriate options of femoral components for revision depend on the degree of femoral bone loss. When the bone loss is minimum, a standard length component can be used like in primary total hip arthroplasty (THA). When it is moderate or severe, special components and techniques would be necessary. Loss of bone stock is the most difficult problem in femoral revision surgery. It increases a risk of complications during operation such as fracture or perforation, and also results in difficulty to achieve stability of the component. Even when the bone defect is moderate or severe, immediate fixation of the femoral component should be mainly supported by native bone. Additionally, in the remaining bone loss, bone tissue is grafted as much as possible. Survival rate of revision arthroplasty is low comparing with that of primary THA. In addition to the present revision, a possible next operation in the future should be considered when we plan revision surgery. Cemented femoral revision has a disadvantage of removal of the prosthesis when it is failed. Removal of cemented component has a high possibility of complications including perforation and fracture. During revision arthroplasty of a cemented femoral component using a modern cement technique, removal of the cement mantle is difficult, time-consuming and hazardous. The cement mass distal to the tip of the femoral component is the most difficult to be removed since it is often well fixed. The removal procedure has a high risk of causing femoral perforation or fracture. Furthermore, in re-revision, the cement fixation will be often beyond the isthmus and into distal bone defect. And revised cemented femoral components would be more difficult to be removed. On the contrary, loosened uncemented components will be removed relatively easily. Uncemented stem has the advantage of bone stock restoration. Simultaneous bone graft induces restoration of bone stock. Restored bone tissue will support the component, and this improvement of the bone stock would be beneficial when it is failed again in the future. According to these principles, we prefer uncemented femoral revisions rather than cemented revisions. This paper will show the clinical results of femoral revisions in our department mainly using an uncemented femoral component

Acetabular osteolysis not infrequently presents the hip surgeon with the daunting and conflicting challenges of bone stock restoration and implant stability. Recognition of the size, position, and extent of the defect preoperatively is necessary for safe navigation of these difficult seas!. Routine radiographic examination is the single most useful preoperative test, as techniques such as CAT scans or MRI examination will be frustrated in the presence of metal-backed devices because of metal artefact. A careful review of the preoperative x-rays will allow the surgeon to properly and accurately anticipate the type of bone defect. Revision of the failed acetabulum when the peripheral rim is intact, with small (< 2 cm) medial defects, and in the absence of large cavitary defects may be reliably managed with simple hemispheric porous ingrowth prostheses, with adjunctive cancellous allograft. However, at least 50% of the prosthesis should be in contact with viable and stable host bone for reliable outcomes. In the absence of this, a revision ring is indicated. The presence of medial wall defects, as indicated by the protrusion of the implant beyond the iliopectineal line on the AP radiograph, indicates the probability of an uncontained central defect. Consideration should be given to the use of a protrusio ring with allograft in these cases, particularly when the defect is larger than 2 cm in diameter. If significant rim defects also exist, the use of a revision cage with allograft in indicated. Rim defects should be suspected in cases of implant “breakout”, or in the presence of implants significantly larger than the apparent diameter of the contralateral acetabulum. Rim defects may contraindicate the use of an oversized porous socket, particularly when more than 2 cm of implant is exposed posterosuperiorly, because of the difficulty in establishing a stable implant-bone interface. In these situations, use of a revision ring is advised. The presence of large “blowout” lesions in the ileum or ischium will indicate the need for substantial quantities of cancellous allograft, which may make the use of a simple porous acetabular shell questionable. Frequently, these lesions will lead to severe peripheral rim defects, requiring the use of a reconstruction ring. Acetabular defects can be recognised reliably with routine radiographs. However, the revision surgeon is advised to be prepared for unanticipated defects by having available reconstruction rings, allograft, and a variety of revision acetabular implants

Bone loss options in revision total knee replacement include prevention (earlier revision before extensive osteolysis, tedious prosthesis removal), prosthetic substitution, and bone grafting. Massive bone loss options include arthrodesis, custom total knee replacement, amputation, or revision with structural allograft-prosthesis composites. Advantages of structural allografts include their biologic potential, versatility (shape to fit host defects), relative cost effectiveness, potential for bone stock restoration, and the potential for ligamentous reattachment. Potential disadvantages include the risk of disease transmission and graft nonunion, malunion, collapse, or resorption. Extensive preoperative planning is required to rule out infection as well as properly select both the type and size of allograft and prosthetic implant. Fresh frozen allograft specimens are most commonly selected due to superior strength. Implant designs with diaphyseal-engaging stems and increased prosthetic constraint are often required. Extensive surgical exposure is often needed including proximal quadricepsplasty or tibial tubercle osteotomy in some cases. Both the host site and allograft require meticulous preparation both to maximise surface contact between host and allograft as well as mechanical interlock of the allograft with the host. Allograft fixation must be rigid to allow for incorporation. Diaphyseal-engaging stems, screws, and/or plates are often required to obtain this. The favoured method of fixation is cementing the prosthesis to the allograft with the addition of diaphyseal- engaging stems into the host medullary canal. Equivalent results have been obtained with either cemented or press-fit stems. Ligamentous reattachment to the allograft is more successful when done via a bone block technique. Wound closure difficulties may be encountered, particularly in the tibial region. Relaxing incision techniques as well as rotational muscle flaps are occasionally necessary to obtain soft tissue closure without excessive tension. Short-term results have shown union rates at greater than 90% when rigid fixation is obtained. In the author’s series of 32 cases, 86% good to excellent results were obtained at an average follow- up period of 50 months. More common complications include instability and graft collapse. Use of more constrained prostheses with long intramedullary stems will lessen these complications

Aims

Robotic-assisted unicompartmental knee arthroplasty (R-UKA) has been proposed as an approach to improve the results of the conventional manual UKA (C-UKA). The aim of this meta-analysis was to analyze the studies comparing R-UKA and C-UKA in terms of clinical outcomes, radiological results, operating time, complications, and revisions.

Partial knee arthroplasty (PKA), either medial or lateral unicompartmental knee artroplasty (UKA) or patellofemoral arthroplasty (PFA) are a good option in suitable patients and have the advantages of reduced operative trauma, preservation of both cruciate ligaments and bone stock, and restoration of normal kinematics within the knee joint. However, questions remain concerning long-term survival. The goal of this review article was to present the long-term results of medial and lateral UKA, PFA and combined compartmental arthroplasty for multicompartmental disease. Medium- and long-term studies suggest reasonable outcomes at ten years with survival greater than 95% in UKA performed for medial osteoarthritis or osteonecrosis, and similarly for lateral UKA, particularly when fixed-bearing implants are used. Disappointing long-term outcomes have been observed with the first generation of patellofemoral implants, as well as early Bi-Uni (ie, combined medial and lateral UKA) or Bicompartmental (combined UKA and PFA) implants due to design and fixation issues. Promising short- and med-term results with the newer generations of PFAs and bicompartmental arthroplasties will require long-term confirmation. Cite this article: Bone Joint J 2015;97-B(10 Suppl A):9–15

Introduction. The advantages of metal on metal (MOM) hip replacement are decreased wear rate, preservation of bone stock, anatomical restoration and enhanced stability. Large amounts of metal wear particles and metal ions are released which may induce adverse reactions including local soft tissue toxicity, hypersensitivity reactions, bone loss and risk of carcinogenesis. Aseptic loosening can be the result of a peri prosthetic osteolysis generated as a result of a biological response to particulate wear debris. Our aim in this study was to determine whether a steeply inclined acetabular component would give rise to a higher concentration of metal ions. Patients and methods. Between April 2003 and June 2006, 22 patients had MOM hip replacement for osteoarthritis by a single Surgeon. There were 12 male and 10 female patients. The average age at the time of surgery was 56 years (Range: 44–69 years). We divided the 22 patients into 2 groups, one group (A) of 11 patients with the acetabular inclination angle more than 50 degrees and the other group (B) of 11 patients with the angle less than 50 degrees. The inclination of the acetabular cup was measured using a standard AP radiograph of the pelvis. The patients had metal ion levels (blood chromium and serum cobalt) measured at an average follow up of 3.2 years (Range 2.4 to 5 years). Results. Mean blood chromium level in the group A (146 nM/L) was significantly higher (p=0.005) than in Group B (92 nM/L). Mean serum cobalt level in the group A (245 nM/L) was significantly higher (p=0.002) than in Group B (110 nM/L). Discussion. The early to mid term published results of MOM hip replacements have been encouraging. There are, however, a number of concerns about the MOM bearing. Although its wear rate is low, it still releases metal ions into the body particularly cobalt and chromium since most metal on metal bearings are made of a cobalt chromium alloy. The long-term consequences of increased levels of these ions in the body are not known. High concentrations of Co and Cr are toxic and are known to interfere with a number of biological functions. There also have been recent reports of soft tissue reactions with MOM hip replacement. In the light of these concerns, it is important to examine factors which may influence the release of metal ions after MOM hip replacement. It has been reported in the recent literature that the position of the acetabular component will influence the bearing wear inturn leading to the release of metal ions after MOM hip replacement. Our findings indicate that steeply inclined acetabular components with an inclination angle greater than 50 degrees gives rise to higher concentration of metal ions

INTRODUCTION. The advantages of large diameter metal on metal total hip arthroplasty (MoM THA) and hip resurfacing arthroplasty are decreased wear rate, preservation of bone stock, anatomical restoration and enhanced stability. Large amounts of metal wear particles and metal ions are released which may induce adverse reactions including local soft tissue toxicity, hypersensitivity reactions, bone loss and risk of carcinogenesis. Aseptic loosening can be the result of a peri-prosthetic osteolysis generated as a result of a biological response to particulate wear debris. No reports in the literature exist as to whether circulating levels of Chromium (Cr) and Cobalt (Co) decrease upon removal of a symptomatic large diameter MoM implant or whether levels remain high due to the effect of metal ions debris left behind in the soft tissues after revision surgery. PATIENTS AND METHODS. Between June 2006 and June 2009 we undertook 44 revision surgeries of both large head MoM THAs (femoral head diameter 38mm) and metal-on-metal hip resurfacings for suspected metallosis. Mean time from original implant to revision was 4 years, 8 months (1yr 4mo–7yr 9mo). The mean follow up evaluation was 2 years and 2 months (1yr 2mo–4 years). Blood samples were taken for whole blood Cr and serum Co according to a recognised protocol and compared with reference levels indicated by the Medicines and Healthcare Regulatory Agency recommendation of less than 7ppb for Cr (130nM/L) and Co (119nM/L). RESULTS. 42 patients were found to have histological evidence of either metal allergy, metal toxicity or foreign body reaction. 2 patients had evidence of infection with no features of metal reaction. 3 patients suffered early dislocation requiring closed reduction. 1 patient had infective complications necessitating Girdlestones. 11 patients were lost to follow up, 8 patients were diagnosed pre operatively on Co and Cr levels in urine or synovial fluid aspirate alone. 23 patients had pre revision blood or serum metal ion level results available for direct comparison. Median serum Co level pre revision was 176.6nM/L, falling post revision to 5.1nM/L (p=<0.001∗). The median whole blood Cr level pre revision was 117nM/L and 19nm/L post revision (p=<0.001∗). Mean Oxford Hip Score was 23.7. DISCUSSION. This study demonstrates that at greater than one year post removal of a large diameter MoM hip implant for the indication of symptomatic metallosis or metal hypersensitivity, metal ion levels fall to almost normal levels and that outcome of revision surgery in terms of patient satisfaction is not adversely affected