Revision total hip arthroplasty (THA) is a challenging scenario following complex primary THA for developmental dysplasia of hip (DDH). Our study envisages the long-term outcomes of revision DDH and the role of lateral structural support in socket fixation in these young patients who may require multiple revisions in their life-time. Hundred and eighteen consecutive cemented revision THAs with minimum follow up of 5 years following primary diagnosis of DDH operated between January 1974 and December 2012 were analysed for their clinical and radiological outcomes. The mean follow-up of 118 patients was 11.0 years (5.1–39.6 years). The Kaplan Mier survivorship at 11 years with end point as revision for any reason was 89.8% (CI 81.1–98.4). Of 118 revisions, 88 acetabular revisions were for aseptic loosening. Out of the acetabular revisions, 21 had pre-existing structural bone grafts from primary surgery, of which only 3 needed structural re-grafting during revision. Amongst the remaining 18 hips, the lateral support from the previous graft facilitated revision with no requirement of additional structural graft. Sixty-three hips did not have any form of grafting during primary operation. Amongst them, 35 had bone grafting in revision surgery (18 structural grafting). This study reports the largest number of revision THAs with primary diagnosis of DDH with the longest follow up. In our experience, the lateral support from the structural graft done in primary operation appears to have provided benefit in subsequent revision socket fixation

Background. Revision total hip arthroplasty (THA) is a challenging scenario following complex primary THA for developmental dysplasia of hip (DDH). This study envisages the long-term outcomes of revision DDH and the role of lateral structural support in socket fixation in these young patients who may require multiple revisions in their life-time. Materials and methods. Hundred and eighteen consecutive cemented revision THAs with minimum follow up of 5 years following primary diagnosis of DDH operated by a single unit between January 1974 and December 2012 were analysed for their clinical and radiological outcomes. Results. The mean follow-up of 118 patients was 11.0 years (5.1–39.6 years). At 11 years, the cumulative survivorship with revision as the endpoint was 89.8%. Amongst the 88 acetabular revisions for aseptic loosening, 21 had pre-existing autologous lateral structural bone graft from the primary THA (group A). Only 3 (14%) of them required lateral structural re-grafting using allograft at revision. With the remaining 18 hips, the lateral support from the previous graft facilitated revision with no requirement of additional structural graft. Sixty-seven hips did not have lateral structural autograft during primary operation (group B). Amongst them, 18 (27%) required lateral structural allograft in revision surgery. Discussion. There is paucity of evidence regarding long-term results following revision THAs in patients with DDH. Nearly double the number of patients with no previous acetabular structural bone graft needed structural allograft during revision in comparison to those patients with autologous structural bone grafting done at primary operation. The lateral structural autograft used at primary arthroplasty seems to provide invaluable bone stock for future revisions. Conclusion. This study reports the largest number of revision THAs with primary diagnosis of DDH with the longest follow up. In our experience, the lateral support from the structural graft done in primary operation appears to have provided benefit in subsequent revision socket fixation

The amount of bone loss due to implant failure, loosening, or osteolysis can vary greatly and can have a major impact on reconstructive options during revision total knee arthroplasty (TKA). Massive bone loss can threaten ligamentous attachments in the vicinity of the knee and may require use of components with additional constraint to compensate for associated ligamentous instability. Classification of bone defects can be helpful in predicting the complexity of the reconstruction required and in facilitating pre-operative planning and implant selection. One very helpful classification of bone loss associated with TKA is the Anderson Orthopaedic Research Institute (AORI) Bone Defect Classification System as it provides the means to compare the location and extent of femoral and tibial bone loss encountered during revision surgery. In general, the higher grade defects (Type IIb or III) on both the femoral and tibial sides are more likely to require stemmed components, and may require the use of either structural graft or large augments to restore support for currently available modular revision components. Custom prostheses were previously utilised for massive defects of this sort, but more recently have been supplanted by revision TKA component systems with or without special metal augments or structural allograft. Options for bone defect management are: 1) Fill with cement; 2) Fill with cement supplemented by screws or K-wires; 3) Morselised bone grafting (for smaller, especially contained cavitary defects); 4) Small segment structural bone graft; 5) Impaction grafting; 6) Large prosthetic augments (cones); 7) Massive structural allograft-prosthetic composites (APC); 8) Custom implants. Maximizing support on intact host bone is a fundamental principle to successful reconstruction and frequently requires extending fixation to the adjacent diaphysis. Pre-operative planning is facilitated by good quality radiographs, supplemented on occasion by additional imaging such as CT. Fluoroscopically controlled x-ray views may assist in diagnosing the loose implant by better revealing the interface between the implant and bone and can facilitate accurate delineation of the extent of bone deficiency present. Part of the pre-operative plan is to ensure adequate range and variety of implant choices and bone graft resources for the planned reconstruction allowing for the potential for unexpected intra-operative findings such as occult fracture through deficient periprosthetic bone. Reconstruction of bone deficiency following removal of the failed implant is largely dictated by the location and extent of bone loss and the quality of bone that remains. While massive bone loss may compromise ligamentous attachment to bone, in the majority of reconstructions the degree of implant constraint needed for proper balancing and restoration of stability is independent of the bone defect. Thus some knees with minimal bone deficiency may require increased constraint due to the status of the soft tissues while others involving very large bone defects especially of the cavitary sort may be well managed with minimal constraint. Highly porous metal augments designed to reestablish metaphyseal support and function in the manner of a prosthetic structural graft have been introduced or are under development by several manufacturers. Published reports of short term experiences have been encouraging for both the tibial side and for femoral augmentation. It remains to be seen whether these implants will provide the desired longer term durability

The major causes of revision total knee are associated with some degree of bone loss. The missing bone must be accounted for to insure success of the revision procedure, to achieve flexion extension balance, restore the joint line to within a centimeter of its previous level, and to assure a proper sizing especially the anteroposterior diameter of the femoral component. In recent years, clinical practice has evolved over time with a general move away from a structural graft with an increase in utilisation of metal augments. Alternatives include cement with or without screw fixation, rarely, with the most common option being the use of metal wedges. With the recent availability of highly porous augments, the role of metal augmentation has increased. Bone graft is now predominantly used in particulate form for contained defects with more limited use of structural graft. The role of the allograft-prosthetic composite has become more limited. For the elderly with osteopenia and massive bone loss, complete metal substitution with an oncology prosthesis has become more common. The degree of bone loss is a major determinant of the management strategy. For contained defects less than 5 mm, cement alone, with or without screw supplementation, may be adequate. For greater than 5 mm, morselised graft is frequently used. For uncontained defects of up to 15 mm or more, metal augmentation is the first choice. Bone graft techniques can be utilised in this setting, however, these are more time consuming and technically demanding with little demonstrated advantage. For larger, uncontained defects, newer generation highly porous augments and step wedges are useful. Large contained defects can be dealt with utilising impaction grafting, similar to the hip impaction grafting technique. Massive distal defects are expeditiously managed with oncology defects in the case of periprosthetic fracture and/or massive osteolysis particularly when combined with osteopenia in an elderly, low demand patient. Surgeons must be familiar with an array of techniques in order to effectively deal with the wide spectrum of bone defects encountered during revision total knee arthroplasty

Aims: to evaluated the radiological evolution of autologous bone graft in acetabular structural and cavitary defects in primary total hip artrhoplasty using an expansion cup (CLS, Sulzer Orthopaedics). Methods: we reviewed, retrospectively, 19 patients (9 males, 10 females, average age 64,7 years) treated in our Unit from January 1994 through July 2000 with acetabular bone grafting. According to the AAOS classiþcation, 11 patients showed a segmental acetabular deþciency requiring a structural graft, 8 had a cavitary defect treated with avoid-þlling bone. X-rays were standardized and investigated for evidence of graft remodelling (obliteration of the interface bone-graft, change in density, bridging trabeculation, reorientation of trabecular pattern) and cupñs loosening (radiolucency, cup migration, ratio graft/cup, breakage of screws). Results: all, but one, patients were evaluated at aminimal follow-up of 2 years (average time 53 month). Osteo-integration was appreciated radiographically at 6 months while union at 12 months in all cases. No cupñs loosening was experienced. Reasorption was evident as a round off and smoothing of the edge of the structural graft in 8 patients while the percentage of bone graft surrounding the cup did not change over time. Conclusions: we believe that the use of an expansion cup, with its elastic properties, allows micro-movements at the interface bone-implant creating a dynamic system that could improve osteo-induction and osteo-integration of the graft

Introduction: Various techniques have been described for cup position in deficient acetabuli. Medialization allows an optimal cup position in the true acetabulum affording cover of the implant in the superolateral area by the bony roof and avoiding the need for a structural graft to cover the protruding lateral edge of the cup. Materials and Methods: During the last 5 years 51 cases of cup medialization have been done during Resurfacing Replacement or THR with hard-hard bearing surfaces (mean follow up 35.2 month). 15 cases were done with the medial acetabuloplasty technique and 36 cases were done by simple over-reaming the medial wall and morselized bone grafting. The mean followed up was 16 months. Surgical technique: Medial Acetabuloplasty: After a cartilage removal, we drill perforations in a horizontal line to weaken the central area of the medial wall. Using an impactor the medial wall is fractured and shifted medially for a few millimeters and the cavitation so produced is filled with morselized bone graft. This technique preserves a shell of bone medially which together with the graft brings about medial bony wall preservation. In extreme acetabular deficiency, this technique is also useful by minimizing the extent of morselized bone grafting needed in the superolateral area for lateral roof bone formation. Results: The medial wall defect was consistently reformed during the first year. In neither the over-reaming with morselized bone graft nor in the group using the medial acetabuloplasty was the stability of the cup compromised. Conclusion: The lateral structural graft techniques are more cumbersome, take more time and the results are less certain. In the short term there was no difference in hip scores or in the radiological assessment between medialization with or without acetabuloplasty. We suggest this technique seems to have the potential for very good long term results

Porous-coated acetabular hemispherical components have proven successful in all but the most severe revision acetabular defects. A revision jumbo porous coated component has been defined as a cup with minimum diameter of 66mm in men and 62mm in women. In published studies this size cup is used in 14–39% of acetabular revisions. The advantages of this technique are ease of use, most deficiencies can be treated without structural graft, host bone contact with the porous surface is maximised, and the hip center is generally normal. Jumbo cups are typically used in Paprosky Type 2, 3A, and many 3B defects. Requirements for success include circumferential acetabular exposure, an intact posterior column, and much of the posterior wall. The cup should be stable with a press-fit between the ischium and anterior superior acetabulum with the addition of some superior lateral support. Additional support is provided with multiple dome or rim screws. Survivorship of the metal shell with revision for any reason has been reported to be 80%-96% at time frames from 15–20 years. The most common post-operative complication is dislocation

Porous-coated acetabular hemispherical components have proven successful in all but the most severe revision acetabular defects. A revision jumbo porous coated component has been defined as cup with minimum diameter of 66 mm in men and 62 mm in women. In published studies this size cup is used in 14–39% of acetabular revisions. The advantages of this technique are ease of use, most deficiencies can be treated without structural graft, host bone contact with the porous surface is maximised, and the hip center is generally normal. Jumbo cups are typically used in Paprosky type 2, 3A, and many 3B defects. Requirements for success include circumferential acetabular exposure, an intact posterior column, and much of the posterior wall. The cup should be stable with a press-fit between the ischium and anterior superior acetabulum with the addition of some superior lateral support. Additional support is provided with multiple dome or rim screws. Survivorship of the metal shell with revision for any reason has been reported to be 80%-96% at time frames from 15–20 years. The most common post-operative complication is dislocation

INTRODUCTION. Porous metal bone fillers are frequently used to manage bony defects encountered in revision total knee arthroplasty (rTKA). Compared to structural graft, porous metal bone fillers have shown significantly lower loosening and failure rates potentially due to osseointegration and increased material strength [1]. The strength of porous metal bone fillers used in lower extremities is frequently assessed using compression/shear/torsion test methods, adapted from spine standards. However, these basic methods may lack clinical relevance, and do not provide any insight on the relationship between patient activity and anticipated prosthesis performance. The goal of this study was to evaluate the response of bone fillers under different activities of daily living, in order to define physiologically relevant worst case biomechanics for component evaluation. METHODS. A bone filler tibial augment is shown in Figure 1. A test construct for tibial augments (half-block each for medial and lateral sides) is shown in Figure 2, along with compatible rTKA components. An additional void in the bone was filled using bone cement. Loading was applied through the tibiofemoral contact patches created on polyethylene tibial insert. Loading was used for two activities of daily living; walking and deep knee bend [2–3]. During walking, the tibiofemoral contact patch on the anterior tibial post gets loaded due to femoral hyperextension with 1.2xbody weight (BW), whereas the medial and lateral condyles get loaded with 3xBW compressive load. For deep knee bend, only the condyles get loaded with 4.34xBW. Compared to walking, 45% higher compressive load magnitude in deep knee bend located further posterior was anticipated to create a larger bending moment and induce higher stress on the half augments. A finite element analysis (FEA) was performed by modeling this test construct with a medium size tibial augment. All components were modeled using linear elastic material properties. All interfaces, including the augment-bone interface (representing full bony ingrowth construct) were modeled using bonded contact. The inferior surface of the bone analogue was constrained. Linear static analyses were performed and peak von mises stress predicted in the tibial augments was compared between activities. RESULTS. Deep knee bend resulted in 31% higher stresses in the tibial augments than for walking. High von mises stresses were mostly predicted at the superior/posterior aspect of the internal side of the augment and in the corners of the cutouts. Figure 3 presents the von mises stresses in the tibial augments for both loading scenarios. DISCUSSION. This study revealed that the 45% increased posterior compressive load associated with deep knee bend is a more significant factor than the moment applied to the post during walking gait for a hyperextended knee, when considering the stress in bone filler augments in revision TKA. The stress in the augments can depend on multiple factors and the proposed FEA method can be used to compare stresses in different porous material bone fillers to determine worst case for assessing its strength

The amount of bone loss due to implant failure, loosening, or osteolysis can vary greatly and can have a major impact on reconstructive options during revision total knee arthroplasty (TKA). Massive bone loss can threaten ligamentous attachments in the vicinity of the knee and may require use of components with additional constraint to compensate for associated ligamentous instability. Classification of bone defects can be helpful in predicting the complexity of the reconstruction required and in facilitating preoperative planning and implant selection. One very helpful classification of bone loss associated with TKA is the Anderson Orthopaedic Research Institute (AORI) Bone Defect Classification System as it provides the means to compare the location and extent of femoral and tibial bone loss encountered during revision surgery. In general, the higher grade defects (Type IIb or III) on both the femoral and tibial sides are more likely to require stemmed components, and may require the use of either structural graft or large augments to restore support for currently available modular revision components. Custom prostheses were previously utilised for massive defects of this sort, but more recently have been supplanted by revision TKA component systems with or without special metal augments or structural allograft. Options for bone defect management are: 1) Fill with cement; 2) Fill with cement supplemented by screws or K-wires; 3) Morselised bone grafting (for smaller, especially contained cavitary defects); 4) Small segment structural bone graft; 5) Impaction grafting; 6) Porous metal cones or sleeves 7) Massive structural allograft-prosthetic composites; 8) Custom implants. Of these, use of uncemented highly porous metal metaphyseal cones in combination with an initial cemented or partially cemented implant has been shown to provide versatile and highly durable results for a range of bone defects including those previously requiring structural bone graft. The hybrid fixation combination of both cement and cementless fixation of an individual tibial or femoral component has emerged as a frequent and often preferred technique. Initial secure and motionless interfaces are provided by the cemented portions of the construct, while subsequent bone ingrowth to the cementless porous metal portions is the key to long term stable fixation. As bone grows into the porous portions there is off loading and protection of the cemented interfaces from mechanical stresses. While maximizing support on intact host bone has been a longstanding fundamental principle of revision arthroplasty, this is facilitated by the use of metaphyseal cones or sleeves in combination with initial fixation into the adjacent diaphysis. Preoperative planning is facilitated by good quality radiographs, supplemented on occasion by additional imaging such as CT. Fluoroscopically controlled x-ray views may assist in diagnosing the loose implant by better revealing the interface between the implant and bone and can facilitate accurate delineation of the extent of bone deficiency present. Part of the preoperative plan is to ensure adequate range and variety of implant choices and bone graft resources for the planned reconstruction allowing for the potential for unexpected intraoperative findings such as occult fracture through deficient periprosthetic bone. While massive bone loss may compromise ligamentous attachment to bone, in the majority of reconstructions, the degree of revision implant constraint needed for proper balancing and restoration of stability is independent of the bone defect. Thus, some knees with minimal bone deficiency may require increased constraint due to the status of the soft tissues while others involving very large bone defects, especially of the cavitary sort, may be well managed with minimal constraint

Porous-coated acetabular hemispherical components have proven successful in all but the most severe revision acetabular defects. A revision jumbo porous coated component has been defined as a cup with minimum diameter of 66 mm in men and 62 mm in women. In published studies this size cup is used in 14% – 39% of acetabular revisions. The advantages of this technique are ease of use, most deficiencies can be treated without structural graft, host bone contact with the porous surface is maximised, and the hip center is generally normal. Jumbo cups are typically used in Paprosky type 2, 3A, and many 3B defects. Requirements for success include circumferential acetabular exposure, an intact posterior column, and much of the posterior wall. The cup should be stable with a press-fit between the ischium and anterior superior acetabulum with the addition of some superior lateral support. Additional support is provided with multiple dome or rim screws. Survivorship of the metal shell with revision for any reason has been reported to be 80% – 96% at time frames from 15 – 20 years. The most common post-operative complication is dislocation

Impaction grafting is an excellent option for acetabular revision. It is technique specific and very popular in England and the Netherlands and to some degree in other European centers. The long term published results are excellent. It is, however, technique dependent and the best results are for contained cavitary defects. If the defect is segmental and can be contained by a single mesh and impaction grafting, the results are still quite good. If, however, there is a larger segmental defect of greater than 50% of the acetabulum or a pelvic discontinuity, other options should be considered. Segmental defects of 25–50% can be managed by minor column (shelf) or figure of 7 structural allografts with good long term results. Porous metal augments are now a good option with promising early to mid-term results. Segmental defects of greater than 50% require a structural graft or porous augment usually protected by a cage. If there is an associated pelvic discontinuity then a cup cage is a better solution. An important question is does impaction grafting facilitate rerevision surgery? There is no evidence to support this but some histological studies of impacted allograft would suggest that it may. On the other hand there are papers that show that structural allografts do restore bone stock for further revision surgery. Also the results of impaction grafting are best in the hands of surgeons comfortable with using cement on the acetabular side, and one of the reasons why this technique is not as popular in North America

The amount of bone loss due to implant failure, loosening, or osteolysis can vary greatly and can have a major impact on reconstructive options during revision total knee arthroplasty (TKA). Massive bone loss can threaten ligamentous attachments in the vicinity of the knee and may require use of components with additional constraint to compensate for associated ligamentous instability. Classification of bone defects can be helpful in predicting the complexity of the reconstruction required and in facilitating pre-operative planning and implant selection. One very helpful classification of bone loss associated with TKA is the Anderson Orthopaedic Research Institute (AORI) Bone Defect Classification System as it provides the means to compare the location and extent of femoral and tibial bone loss encountered during revision surgery. In general, the higher grade defects (Type IIb or III) on both the femoral and tibial sides are more likely to require stemmed components, and may require the use of either structural graft or large augments to restore support for currently available modular revision components. Custom prostheses were previously utilised for massive defects of this sort, but more recently have been supplanted by revision TKA component systems with or without special metal augments or structural allograft. Options for bone defect management are: 1) Fill with cement; 2) Fill with cement supplemented by screws or K-wires; 3) Morselised bone grafting (for smaller, especially contained cavitary defects); 4) Small segment structural bone graft; 5) Impaction grafting; 6) Large prosthetic augments (cones); 7) Massive structural allograft-prosthetic composites (APC); 8) Custom implants. Maximizing support on intact host bone is a fundamental principle to successful reconstruction and frequently requires extending fixation to the adjacent diaphysis. Pre-operative planning is facilitated by good quality radiographs, supplemented on occasion by additional imaging such as CT. Fluoroscopically controlled x-ray views may assist in diagnosing the loose implant by better revealing the interface between the implant and bone and can facilitate accurate delineation of the extent of bone deficiency present. Part of the pre-operative plan is to ensure adequate range and variety of implant choices and bone graft resources for the planned reconstruction allowing for the potential for unexpected intra-operative findings such as occult fracture through deficient periprosthetic bone. Reconstruction of bone deficiency following removal of the failed implant is largely dictated by the location and extent of bone loss and the quality of bone that remains. While massive bone loss may compromise ligamentous attachment to bone, in the majority of reconstructions the degree of implant constraint needed for proper balancing and restoration of stability is independent of the bone defect. Thus some knees with minimal bone deficiency may require increased constraint due to the status of the soft tissues while others involving very large bone defects especially of the cavitary sort may be well managed with minimal constraint

Important issues related to total hip replacement for dysplasia are: placement of the cup and bone stock; the role of femoral osteotomy, and the choice of acetabular and femoral components. The cup can be placed at the correct or near correct anatomical level with or without a bone graft, in a high position (high hip center) or at the right level in a protruded position. All three techniques can provide adequate coverage of the cup. In the high hip position bone graft is not usually necessary to obtain cup coverage. There is however a higher rate of component loosening, a higher dislocation rate, and lengthening is limited to the femoral side. Placing the cup in a protruded position to obtain coverage does not restore bone stock for future surgery, but it does place the hip at the correct level. Placing the cup in the correct anatomical position (i.e. at the right level and not protruded) may require a structural autograft which adds to the complexity of the case. However, bone stock is restored for future surgery. In a radiographic study of 31 shelf grafts with an average follow-up of 14 years, 22 grafts had mild resorption, and 9 moderate resorption. Ten patients required cup revision, 2 at 9 years, 2 at 10 to 15 years, and 6 at over 15 years. Only 2 hips required another structural graft. Femoral osteotomy may be used as part of the exposure for diaphyseal shortening or for derotation of excessive anteversion. The osteotomy is carried out in the sub-trochanteric region and may be oblique, step-cut or transverse. Fixation of the osteotomy is achieved via the stem, a plate, or a cortical strut. Cementless components are usually used because of the relatively young age of this patient population. Small components may be necessary. On the femoral side, the stem should be straight or modular so excessive anteversion can be neutralised

The amount of bone loss due to implant failure, loosening, or osteolysis can vary greatly and can have a major impact on reconstructive options during revision total knee arthroplasty (TKA). Massive bone loss can threaten ligamentous attachments in the vicinity of the knee and may require use of components with additional constraint to compensate for associated ligamentous instability. Classification of bone defects can be helpful in predicting the complexity of the reconstruction required and in facilitating pre-operative planning and implant selection. One very helpful classification of bone loss associated with TKA is the Anderson Orthopaedic Research Institute (AORI) Bone Defect Classification System as it provides the means to compare the location and extent of femoral and tibial bone loss encountered during revision surgery. In general, the higher grade defects (Type IIb or III) on both the femoral and tibial sides are more likely to require stemmed components, and may require the use of either structural graft or large augments to restore support for currently available modular revision components. Custom prostheses were previously utilised for massive defects of this sort, but more recently have been supplanted by revision TKA component systems with or without special metal augments or structural allograft. Options for bone defect management are: 1) Fill with cement; 2) Fill with cement supplemented by screws or K-wires; 3) Morselised bone grafting (for smaller, especially contained cavitary defects); 4) Small segment structural bone graft; 5) Impaction grafting; 6) Large prosthetic augments (cones); 7) Massive structural allograft-prosthetic composites (APC); 8) Custom implants. Maximizing support on intact host bone is a fundamental principle to successful reconstruction and frequently requires extending fixation to the adjacent diaphysis. Pre-operative planning is facilitated by good quality radiographs, supplemented on occasion by additional imaging such as CT. Fluoroscopically controlled x-ray views may assist in diagnosing the loose implant by better revealing the interface between the implant and bone and can facilitate accurate delineation of the extent of bone deficiency present. Part of the pre-operative plan is to ensure adequate range and variety of implant choices and bone graft resources for the planned reconstruction allowing for the potential for unexpected intra-operative findings such as occult fracture through deficient periprosthetic bone. Reconstruction of bone deficiency following removal of the failed implant is largely dictated by the location and extent of bone loss and the quality of bone that remains. While massive bone loss may compromise ligamentous attachment to bone, in the majority of reconstructions the degree of implant constraint needed for proper balancing and restoration of stability is independent of the bone defect. Thus some knees with minimal bone deficiency may require increased constraint due to the status of the soft tissues while others involving very large bone defects especially of the cavitary sort may be well managed with minimal constraint

Aims

Post-traumatic periprosthetic acetabular fractures are rare but serious. Few studies carried out on small cohorts have reported them in the literature. The aim of this work is to describe the specific characteristics of post-traumatic periprosthetic acetabular fractures, and the outcome of their surgical treatment in terms of function and complications.

The amount of bone loss due to implant failure, loosening, or osteolysis can vary greatly and can have a major impact on reconstructive options during revision total knee arthroplasty (TKA). Massive bone loss can threaten ligamentous attachments in the vicinity of the knee and may require use of components with additional constraint to compensate for associated ligamentous instability. Classification of bone defects can be helpful in predicting the complexity of the reconstruction required and in facilitating preoperative planning and implant selection. One very helpful classification of bone loss associated with TKA is the Anderson Orthopaedic Research Institute (AORI) Bone Defect Classification System as it provides the means to compare the location and extent of femoral and tibial bone loss encountered during revision surgery. In general, the higher grade defects (Type IIb or III) on both the femoral and tibial sides are more likely to require stemmed components, and may require the use of either structural graft or large augments to restore support for currently available modular revision components. Custom prostheses were previously utilised for massive defects of this sort, but more recently have been supplanted by revision TKA component systems with or without special metal augments or structural allograft. Options for bone defect management are: 1) Fill with cement; 2) Fill with cement supplemented by screws or K-wires; 3) Morselised bone grafting (for smaller, especially contained cavitary defects); 4) Small segment structural bone graft; 5) Impaction grafting; 6) Large prosthetic augments (cones); 7) Massive structural allograft-prosthetic composites (APC); 8) Custom implants. Maximising support on intact host bone is a fundamental principle to successful reconstruction and frequently requires extending fixation to the adjacent diaphysis. Preoperative planning is facilitated by good quality radiographs, supplemented on occasion by additional imaging such as CT. Fluoroscopically controlled x-ray views may assist in diagnosing the loose implant by better revealing the interface between the implant and bone and can facilitate accurate delineation of the extent of bone deficiency present. Part of the preoperative plan is to ensure adequate range and variety of implant choices and bone graft resources for the planned reconstruction allowing for the potential for unexpected intraoperative findings such as occult fracture through deficient periprosthetic bone. Reconstruction of bone deficiency following removal of the failed implant is largely dictated by the location and extent of bone loss and the quality of bone that remains. While massive bone loss may compromise ligamentous attachment to bone, in the majority of reconstructions the degree of implant constraint needed for proper balancing and restoration of stability is independent of the bone defect. Thus some knees with minimal bone deficiency may require increased constraint due to the status of the soft tissues while others involving very large bone defects especially of the cavitary sort may be well managed with minimal constraint

The goals of revision arthroplasty of the hip are to restore the anatomy and achieve stable fixation for new acetabular and femoral components. It is important to restore bone stock, thereby creating an environment for stable fixation for the new components. The bone defects encountered in revision arthroplasty of the hip can be classified either as contained (cavitary) or uncontained (segmental). Contained defects on both the acetabular and femoral sides can be addressed by morselised bone graft that is compacted into the defect. Severe uncontained defects are more of a problem particularly on the acetabular side where bypass fixation such as distal fixation on the femoral side is not really an alternative. Most authors agree that the use of morselised allograft bone for contained defects is the treatment of choice as long as stable fixation of the acetabular component can be achieved and there is a reasonable amount of contact with bleeding host bone for eventual ingrowth and stabilisation of the cup. On the femoral side, contained defects can be addressed with impaction grafting for very young patients or bypass fixation in the diaphysis of the femur using more extensively coated femoral components or taper devices. Segmental defects on the acetabular side have been addressed with structural allografts for the past 15 to 20 years. These are indicated in younger individuals with Type 3A defects. Structural grafts are unsuccessful in Type 3B defects. Alternatives to the structural allografts are now being utilised with shorter but encouraging results in most multiply operated hips with bone loss. New porous metals such as trabecular metal (tantalum), which has a high porosity similar to trabecular bone and also has a high coefficient of friction, provide excellent initial stability. The porosity provides a very favorable environment for bone ingrowth and bone graft remodeling. Porous metal acetabular components are now more commonly used when there is limited contact with bleeding host bone. Porous metal augments of all sizes are being used instead of structural allografts in most situations. On the femoral side, metaphyseal bone loss, whether contained or uncontained, is most often addressed by diaphyseal fixation with long porous or tapered implants, modular if necessary. Distal fixation requires at least 4 centimeters of diaphyseal bone and in Type IV femurs, a choice must be made between a mega prosthesis or a proximal femoral allograft. The proximal femoral allograft can restore bone stock for future surgery in younger patients. The mega prosthesis which is more appropriate in the older population may require total femoral replacement if there is not enough diaphyseal bone for distal fixation with cement. Cortical struts are used for circumferential diaphyseal bone defects to stabilise proximal femoral allografts, to bypass stress risers and to serve as a biological plate for stabilising peri-prosthetic fractures

Purpose: Pelvic discontinuity associated with bone loss is a complex challenge in acetabular revision surgery. Reconstruction with anti protrusion cages, Trabecular Metal (Zimmer, Warsaw, Indiana) cups and morselized bone (Cup-Cage) constructs is a relatively new technique used by the authors for the past 6 years. The purpose of the study was to examine the clinical outcome of these patients. Method: Thirty-two consecutive acetabular revision reconstructions in 30 patients with pelvic discontinuity and bone loss treated by cup cage technique between January 2003 and September 2007 were reviewed. Average clinical and radiological follow up was 38.5 ± 19 months (range 12 – 68, median 34.5). Failure was defined as component migration > 5mm. Results: In 29 (90.6%) patients there was no clinical or radiographic evidence indicative of loosening at latest follow up. Harris Hip Scores improved significantly (p< 0.001) from 46.6 ± 10.4 to 78.7 ± 10.4 at 2 year follow up. In 3 patients the construct migrated at 1 year post surgery. One construct was revised to anti protrusion cage with a structural graft while the other was revised to a large Trabecular Metal cup. The third patient is scheduled for revision. Complications included 2 dislocations, 1 infection and 1 partial peroneal nerve palsy. Two patients died due to unrelated reasons at 1 and 3 years post surgery, respectively. Conclusion: Treatment of pelvic discontinuity by Cup-Cage construct is a reliable option based on preliminary results which suggest restoration of the pelvic mechanical stability. However, patients should be followed closely in order to detect cup migration until satisfactory bony ingrowth into the cup takes place

The uncemented cup with iliac stem ensures immediate primary stability by fixation to the hipbone in acetabular loosening with severe bone defect. Homologous bone grafts contribute to restoring bone stock, which is a fundamental requirement for long lasting implant stability. From 2002 to 2004 we implanted 23 cups with iliac stems in 22 patients. In 7 cases there was also stem loosening, and so total hip arthroplasty was performed. In 2 patients the defect was grade 2b, in 5 grade 3a, and in 16 grade 3b according to Paprosky. A direct lateral approach was performed in the supine position. Morselized bone grafts were used in all cases by the “impaction grafting” technique, and in 4 cases modelled structural grafts were also employed. Mean follow-up has been 18 months (8–32). So far we have not had any cases of loosening. At follow-up x-rays showed remodelling of the grafts with integration. The cup with iliac stem enables primary stability on healthy bone tissue, and protects the grafts form mechanical stimulation, thus allowing them to integrate and restore bone-stock. It also restores the centre of rotation, and provides functional benefits and implant stability