Total knee replacement (TKR) is one of the most successful procedures in orthopaedic surgery. Although originally limited to more elderly and less active individuals, the inclusion criteria for TKR have changed, with ever younger, more active and heavier patients receiving TKR.

Initially, tibial components were cemented all-polyethylene monoblock constructs. Subsequent long-term follow-up studies of these implants have demonstrated excellent durability in survivorship studies out to 20 years. Aseptic loosening of the tibial component was one of the main causes of failure in these implants. Polyethylene wear with osteolysis around well-fixed implants was rarely (if ever) observed. Cemented metal-backed nonmodular tibial components were subsequently introduced to allow for improved tibial load distribution and to protect osteoporotic bone. Long-term studies have established that many one-piece nonmodular tibial components have maintained excellent durability.

Eventually, modularity between the polyethylene tibial component and the metal-backed tray was introduced in the mid-80s mainly to facilitate screw fixation for cementless implants. These designs also provided intra-operative versatility by allowing interchange of various polyethylene thicknesses, and also aided the addition of stems and wedges. Other advantages included the reduction of inventory, and the potential for isolated tibial polyethylene exchanges.

Since the late 1980's, the phenomena of polyethylene wear and osteolysis have been observed much more frequently when compared with earlier eras. The reasons for this increased prevalence of synovitis, progressive osteolysis, and severe polyethylene wear remain unclear, but there is no question that it was associated with the widespread use of both cementless and cemented modular tibial designs.

Mayo Data: Modular versus All Polyethylene Tibial Components in Primary TKA: The study population included 10,601 adult (>18 years) patients with 14,524 primary TKR procedures performed at our institution between 1/1/1988 and 12/31/2005. Mean age was 68.7 years and 55% were female. Overall revision rates and revisions for loosening, wear/osteolysis were compared across different designs using Cox proportional hazards regression models adjusting for age, sex, calendar year and body mass index (BMI). Over an average 9 years follow-up, a total of 865 revisions, including 252 tibia revisions were performed, corresponding to overall survival of 89% (Confidence intervals (CI): 88%, 90%) at 15 years. In comparison to metal modular designs, risk of tibial revision was significantly lower with all-poly tibias (HR 0.3, 95% CI: 0.2, 0.5). Overall, posterior cruciate-retaining (CR) designs performed better than the posterior-stabilised (PS) designs (p=0.002). With any revision as the endpoint, there were no significant differences across the 18 designs examined. Similarly, there were no significant differences across the 18 designs when we considered revisions for aseptic loosening, wear, and osteolysis. Among patient characteristics, male gender, younger age, higher BMI were all significantly associated with higher risk of revisions (p<0.008).

Available data support the use of nonmodular tibial designs in TKR in order to prevent or reduce the chance of backside wear, third body particles from resulting metallic debris and associated polyethylene induced osteolysis. In all patients, (not just older individuals) use of an all polyethylene tibial component is an attractive and more cost effective alternative, and is associated with the best survivorship and lowest risk of revision.

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.

There are many types of articulating surfaces in uncemented acetabular cups. Most of the designs currently available are modular, with the shell snapping into a locking mechanism of some type. An Elliptical Monoblock design has been available for 15 years and was originally made of titanium with a factory assembled compression molded polyethylene liner. Porous tantalum (trabecular metal) was used as the shell material in a subsequent more recent design and in this design the polyethylene is actually molded directly into the tantalum framework.

Monoblock acetabular components do not allow particulate access to the ilium via screw holes and require no surgeon assembled locking mechanism which may increase backside wear and metallic debris. There are no holes in the socket because of the monoblock construct. Because of this absence of screw holes there is an inability to visualise the floor of the acetabulum and perfect coaptation between the shell and the acetabular floor may not occur. The presence of dome gaps of greater than 1.5mm have been noted in 5% of these components but these have not compromised implant stability and in a review of over 600 cups there has been no change in implant position. The Elliptical shape of the cup makes the mouth of the acetabular component 2mm greater than the dome so that an exceptionally strong acetabular rim fit results.

Results will be reported from two major institutional series with a minimum 10-year follow-up (range 10–15 years). No pelvic osteolysis was not seen in any patient in either series. In the HSS series of 250 cases with minimum 10 year follow up there were 4 revisions for instability but none for mechanical failure. There were three femoral revisions for loosening but the cup was intact and not revised in these patients. Utilising the Livermore measurement method polyethylene wear averages 0.8mm per year (0.6mm-1.3mm) and there have been no revisions for wear. Radiographic evaluation demonstrates stable bony interface in all patients. In a Mayo series of prospectively randomised patients also at minimum 10 years there was no lysis and only one case of aseptic loosening in a beaded titanium cup. At minimum 10-year follow up two similar elliptical monoblock cementless acetabular component designs with compression molded polyethylene have confirmed the theoretical advantages of this design concept and demonstrate long term results that have been excellent to date.

Complications involving the knee extensor mechanism occur in 1% to 12% of patients following total knee arthroplasty (TKA), and have negative effects on patient outcomes. While multiple reconstruction options have been described for complete disruption of the extensor mechanism, the results in patients with a prior TKA are inferior to those in patients without a TKA, and frequently have required the use of allograft tendon grafts which can attenuate and stretch over time. However, encouraging results have been reported by Browne and Hanssen in treatment of patellar tendon disruption with the use of a synthetic mesh (knitted monofilament polypropylene). In this technique, a synthetic graft is created by folding a 10 × 14 inch sheet of mesh and securing it with non-absorbable sutures. A burr is then used to create a trough in the anterior aspect of the tibia to accept the mesh graft. The graft is inserted into the trough and secured with cement. After the cement cures, a transfixion screw with a washer is placed. A portal is subsequently created in the soft tissues lateral patellar tendon remnants to allow delivery of the graft from deep to superficial. The patella and quadriceps tendon are mobilised, and the graft is secured with sutures to the lateral retinaculum, vastus lateralis, and quadriceps tendon. The vastus medialis is then mobilised and brought in a pants-over-vest manner over the mesh graft, and secured with additional sutures. Finally, the distal arthrotomy is closed tightly to completely cover the mesh graft with host tissue. In their series, Browne and Hanssen noted that 9 of 13 patients achieved an extensor lag of <10 degrees with preserved knee flexion and significant improvements in the mean Knee Society scores for pain and function. A similar modified method has been used at our institution for chronic quadriceps tendon disruptions as well. The reconstructions have shown less of a tendency to late attenuation, stretch and recurrent extensor lag beyond two years compared to our experience with tendon allograft reconstructions and remains our procedure of choice at our institution for the majority of these challenging problems.

Fracture of the acetabulum can result in damage to the articular surface that ranges from minimal to catastrophic. Hip arthroplasty may be required for more severe injuries due to marked articular surface damage, post traumatic degenerative changes, persistent malunion or nonunion, or occasionally avascular necrosis and destruction of the femoral head. These problems may be seen following both closed and open fracture treatment, but prior open reduction and internal fixation often makes subsequent THA more difficult due to soft tissue scarring and retained hardware. In select acute acetabular fracture cases with severe initial comminution of the joint, open reduction and fixation can be technically impossible or so clearly destined to early failure that initial fracture treatment with combined limited fixation and simultaneous THA is the best option, especially in osteoporotic elderly fracture patients.

Problems which may be encountered during any THA in a patient with a prior acetabular fracture include: difficult exposure due to soft tissue defects and scarring, presence of heterotopic ossification, and nerve palsy from the original fracture or subsequent osteosynthesis. Retained hardware can present significant challenges and frequently is left in place or removed in part or completely, when intraarticular in location or blocking preparation of the acetabular cavity and placement of the cup. Additional potential problems include residual deformity and malunion, persistent pelvic dissociation or nonunion of fracture fragments, cavitary or segmental bone loss from displaced or resorbed bone fragments, and occasionally occult deep infection.

Preoperative assessment and planning should include careful consideration of the most appropriate surgical approach, which may be impacted by the need for hardware removal. Screening laboratory studies and aspiration of the hip may prove helpful in excluding associated deep infection. Intraoperative sciatic nerve monitoring may be of assistance in patients with partial residual nerve deficits or where extensive posterior exposure and mobilization of the sciatic nerve is needed for hardware removal or excision of heterotopic ossification. Metal cutting tools to allow partial removal of long plates and adjunctive equipment for removal of broken or stripped screws should be routinely available during these cases. Careful preoperative planning regarding implant and reconstructive options can also ensure availability of proper components and equipment. Often implants and techniques developed for revision surgery for management of major bone deficiencies are needed.

Reported results suggest that surgery is frequently prolonged, can be associated with greater blood loss and may result in increased risk of post-arthroplasty heterotopic ossification when compared to routine primary procedures. Bone stock and fracture union may be better in patients with prior internal fixation than in those with nonoperative treatment of major displaced acetabular fractures. Available long-term results document more durable results with lower rates of aseptic loosening with uncemented acetabular fixation compared to cemented acetabular components. These patients are at higher risk of revision and failure than patients undergoing THA for simple osteoarthritis, though initial short-term results are comparable to conventional hip arthroplasty patients, as long as early wound healing problems and deep infection can be avoided, which is a greater risk for acute THA for initial fracture care. The application of newer implant designs, highly porous ingrowth materials, and methods for management of acetabular bone deficiency developed for revision THA have helped improve results in this challenging subset of primary THA patients.

Total knee replacement is one of the most successful procedures in orthopaedic surgery. Although originally limited to more elderly and less active individuals, the inclusion criteria have changed, with ever younger, more active and heavier patients receiving TKA. Currently, wear debris related osteolysis and associated prosthetic loosening are major modes of failure for TKA implants of all designs.

Initially, tibial components were cemented all polyethylene monoblock constructs. Subsequent long-term follow-up studies of these implants have demonstrated excellent durability in survivorship studies out to twenty years. Aseptic loosening of the tibial component was one of the main causes of failure in these implants. Polyethylene wear with osteolysis around well fixed implants was rarely (if ever) observed. Cemented metal-backed nonmodular tibial components were subsequently introduced to allow for improved tibial load distribution and to protect osteoporotic bone. Long-term studies have established that many one-piece nonmodular tibial components have maintained excellent durability. Eventually, modularity between the polyethylene tibial component and the metal-backed tray was introduced in the mid-80s mainly to facilitate screw fixation for cementless implants. These designs also provided intraoperative versatility by allowing interchange of various polyethylene thicknesses, and also aided the addition of stems and wedges. Since the late 1980's, the phenomena of polyethylene wear and osteolysis have been observed much more frequently when compared with earlier eras. The reasons for this increased prevalence of synovitis, progressive osteolysis, and severe polyethylene wear remain unclear, but there is no question that it was associated with the widespread use of both cementless and cemented modular tibial designs.

Mayo Data: Modular versus All Polyethylene Tibial Components in Primary TKA

The study population included 10,601 adult (>18 years) patients with 14,524 primary TKA procedures performed at our institution between 1/1/1988 and 12/31/2005. Mean age was 68.7 years and 55% were female. Overall revision rates and revisions for loosening, wear/osteolysis were compared across different designs using Cox proportional hazards regression models adjusting for age, sex, calendar year and body mass index (BMI). Over an average 9 years follow-up, a total of 865 revisions, including 252 tibia revisions were performed, corresponding to overall survival of 89% (Confidence intervals (CI): 88%, 90%) at 15 years. In comparison to metal modular designs, risk of tibial revision was significantly lower with all-poly tibias (HR 0.3, 95% CI: 0.2, 0.5). Overall, posterior cruciate-retaining (CR) designs performed better than the posterior-stabilised (PS) designs (p=0.002). With any revision as the endpoint, there were no significant differences across the 18 designs examined. Similarly, there were no significant differences across the 18 designs when we considered revisions for aseptic loosening, wear, osteolysis. Among patient characteristics, male gender, younger age, higher BMI were all significantly associated with higher risk of revisions (p<0.008).

Summary: Available data support the use of nonmodular tibial designs in TKA in order to prevent or reduce the chance of backside wear, third body particles from resulting metallic debris and associated polyethylene induced osteolysis. In all patients, (not just older individuals) use of an all polyethylene tibial component is an attractive and more cost effective alternative, and is associated with the best survivorship and lowest risk of revision.

Total knee replacement is one of the most successful procedures in orthopaedic surgery. Although originally limited to more elderly and less active individuals, the inclusion criteria for TKA have changed, with ever younger, more active and heavier patients receiving TKA. Initially, tibial components were cemented all polyethylene monoblock constructs. Subsequent long-term follow-up studies of these implants have demonstrated excellent durability in survivorship studies out to twenty years. Aseptic loosening of the tibial component was one of the main causes of failure in these implants. Polyethylene wear with osteolysis around well fixed implants was rarely (if ever) observed. Cemented metal-backed nonmodular tibial components were subsequently introduced to allow for improved tibial load distribution and to protect osteoporotic bone. Long-term studies have established that many one-piece nonmodular tibial components have maintained excellent durability.

Eventually, modularity between the polyethylene tibial component and the metal-backed tray was introduced in the mid-80s mainly to facilitate screw fixation for cementless implants. These designs also provided intraoperative versatility by allowing interchange of various polyethylene thicknesses, and to also aided the addition of stems and wedges. Other advantages included the reduction of inventory, and the potential for isolated tibial polyethylene exchanges as a simpler revision procedure. However several studies have documented the high failure rate of isolated polyethylene exchange procedures, probably because technical problems related to the original components are left uncorrected. Since the late 1980's, the phenomena of polyethylene wear and osteolysis has been observed much more frequently when compared with earlier eras. The reasons for this increased prevalence of synovitis, progressive osteolysis, and severe polyethylene wear remain unclear, but there is no question that it was associated with the widespread use of both cementless and cemented modular tibial designs.

Mayo Data: Modular versus All Polyethylene Tibial Components in Primary TKA. The study population included 10,601 adult (>18 years) patients with 14,524 primary TKA procedures performed at our institution between 1/1/1988 and 12/31/2005. Mean age was 68.7 years and 55% were female. Overall revision rates and revisions for loosening, wear/osteolysis were compared across different designs using Cox proportional hazards regression models adjusting for age, sex, calendar year and body mass index (BMI). Over an average 9 years follow-up, a total of 865 revisions, including 252 tibia revisions were performed, corresponding to overall survival of 89% (Confidence intervals (CI): 88%, 90%) at 15 years. In comparison to metal modular designs, risk of tibial revision was significantly lower with all-poly tibias (HR 0.3, 95% CI: 0.2, 0.5). Overall, posterior cruciate-retaining (CR) designs performed better than the posterior-stabilised (PS) designs (p=0.002). With any revision as the endpoint, there were no significant differences across the 18 designs examined. Similarly, there were no significant differences across the 18 designs when we considered revisions for aseptic loosening, wear, osteolysis. Among patient characteristics, male gender, younger age, higher BMI were all significantly associated with higher risk of revisions (p<0.008).

Available data support the use of nonmodular tibial designs in TKA in order to prevent or reduce the chance of backside wear, third body particles from resulting metallic debris and associated polyethylene induced osteolysis. In most patients, but particularly in older patients use of an all polyethylene tibial component is not only more cost effective, but is associated with the best survivorship and lowest risk of revision.

Over the past 40 years information from large institutional total joint registries have aided in patient clinical care and follow-up efforts, have helped drive improvements in clinical practice, and have been a powerful tool for generating research studies on large well documented populations of patients. Still, these efforts are limited in that they are expensive, usually reflect a single institutional experience, and results can be biased by the larger volumes or experience at the typically large academic centers which have such registries in place.

National registry efforts in other countries including Scandinavia, Australia, and the UK have resulted in improved outcomes and a decreased number of revision procedures by a combination of early identification and withdrawal of poorly performing implants, altered surgical techniques, implant choices and behaviors by surgeons, changes in practices by hospitals, and modification in requirements and incentives by payors and regulatory agencies.

The American Joint Replacement Registry (AJRR) is a collaborative multi-stakeholder, independent, not-for-profit 501 c3 organisation established in 2009 for data collection and quality improvement initiatives relating to total hip and knee arthroplasty. AJRR is a national registry effort with the goal of enrolling more than 90% of the over 5,000 hospitals performing nearly 1 million hip and knee arthroplasties each year in the US. AJRR is supported by contributions from the American Academy of Orthopedic Surgeons (AAOS), the American Association of Hip and Knee Surgeons (AAHKS), the Hip Society, the Knee Society, Health Insurers, Medical Device Manufacturers, and individual orthopaedic surgeons via designated contributions through the Orthopedic Research and Education Foundation (OREF).

The overarching goal of AJRR is to improve arthroplasty care for patients through the collection and sharing of data on all primary and revision total joint replacement procedures in the U.S. The mission of the registry is to enhance patient safety, and improve the value of arthroplasty care. This will be accomplished by providing national benchmarks for implant, surgeon and hospital performance which serves to modify behaviors thereby decreasing the revision burden, improving outcomes and reducing costs.

From the time of incorporation in 2009 up to October 2013 the AJRR has secured the participation of 218 hospitals in 47 different states in the formal enrollment process, and have level one data submission from more than 100 institutions on over 63,000 hip and knee procedures.

In addition to publicly available annual reports, confidential specific individual reports for hospitals, surgeons and manufacturers will be available by subscription with an option for future confidential online direct data queries by an individual or entity regarding their own individual performance compared to national benchmark values.

In summary, registry studies have provided a rich source of information for improving arthroplasty care over the past four decades, with the emergence and increasing interaction of national registries a major factor in current efforts to increase both the quality and value of the health care of entire populations. The development, support and continued expansion of a national registry in the US must remain a central focus if we wish to improve as much as possible the arthroplasty care provided to all patients in our country.

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. 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. This system 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 as follows: 1) fill with cement, 2) fill with cement supplemented by screws or K-wires, 3) Morsellised 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.

It is very helpful for revision surgeons to have a variety of reconstructive options available, even despite a well thought-out preoperative plan. Preoperative planning is important but the plan that results may require alteration during the course of the surgery to accommodate bone defects which are either less or more severe than thought pre-operatively, and to adjust to variable quality and extent of host bone remaining, as this provides the mechanical platform for the reconstruction. Maximising support on intact host bone is a fundamental principle to successful reconstruction and frequently requires extending fixation to the adjacent diaphysis.

Bone defect management during revision total knee arthroplasty can provide a wide range of challenges from relatively trivial problems with small defects manageable with cement or small amounts of cancellous graft to massive deficiencies that may defy reconstruction except with allograft prosthetic components or large segmental replacing tumor-type implants. The more common Type II deficiencies increasingly seen in the context of particulate driven osteolysis demand a wide range of implant and bone graft options so that an individualised reconstruction can be accomplished for that particular patient based on bone defect size, location, quality of bone remaining, ligamentous status, and anticipated patient demands.

Introduction

Recurrent instability after total hip arthroplasty remains a serious and somewhat frequent problem. Constrained implants have proven effective to manage instability. This has led to a liberal utilization of these devices. However, sporadic mechanical failures have been reported. This report analyzes the failures of a single constrained device at our institution.

Introduction: Dislocation following total knee arthroplasty (TKA) is an unusual but dramatic post-operative complication. Previously reports involve only a few isolated cases. This study retrospectively analyzed the incidence, associated factors and treatment of dislocation following TKA.

Method: All cases of TKA dislocation since 1970, when the first TKA was done at our institution, were identified from our institutional total joint registry (31.000 TKA). The medical history and X-ray were reviewed on all cases with this diagnosis. The 58 cases identified were reviewed with particular attention to associated factors that might contribute to this problem.

Results: The overall incidence of TKA dislocation was 1.87 per 1.000 arthroplasties, with a rate of 0.93 and 6.61 for primary and revision TKA respectively. The dislocations occurred at the mean of 29.5 months (range 0 to 193). Original prosthesis designs used were posterior-stabilized (53%), cruciate retaining (31%) and rotating hinge (16%). Dislocation was associated with a history of ligament laxity in 45.6% of patients, extensor mechanism deficiency in 35.5% and TKA infection in 25.9%. The mean follow-up post dislocation was 4.8 years (range 0.1 to 20.1). Non operative treatment was used for 29 knees and resulted in 25 knees experiencing further symptomatic instability. The remaining knees were treated by surgery. Of those treated by revision TKA (N=27) only 3 complained of symptomatic instability (P< 0.001).

Conclusions: TKA dislocation is a major complication. Conservative treatment is ineffective. Revision TKA reliably yields a stable knee in 89% of cases so treated. These results emphasize the importance of proper surgical technique, careful soft tissue balancing, and adequate constraint in the prevention and treatment of this problem.

We report a series of sixteen total hip arthroplasties utilizing a porous tantalum trabecular metal acetabular component in patients with tumors of the hip.

The study included eight men and eight women with an average age of 59.3 (range 22–80 years). Two patients had benign but locally recurrent disease destructive of bone (Langerhan’s Cell Histiocytosis and Rosi Dorfman Disease), while fourteen had malignant lesions. The latter included six myeloma, two lymphoma, and six metastatic carcinoma (three breast, one prostate, one lung, and one unknown site). Fifteen patients had prior radiation therapy. The technique used was determined by the extent of the lesion and the quality of remaining host bone.

In eight patients major deficiencies necessitated augmentation of the porous tantalum cup with an anti-protrusio device “over -the top” a cup-cage construct. Porous tantalum augments were utilised with the cup to fill defects in the acetabulum in seven patients. Postoperative complications were seen in four cases (DVT, DIC, pneumonia, and one death from c. difficile colitis).

Postoperatively, the majority of the patients had excellent pain relief and improved ambulatory status. No clinical failures have been observed at follow-up (mean 12.5 months, range twenty days-twenty-eight months). There have been no re-operations. Radiographically, no migration or evidence of implant loosening has been observed.

Purpose of the study: The majority of acetabular bone defects observed during revision hip surgery can be treated with a hemispheric implant, associated or not with a bone graft. In many patients however, loss of bone stock is so great that a more complex system must be used with a sustaining ring, multilobulated implants, or massive allografts. All have their technical difficulties or problems with fixation. The purpose of this work was to evaluate a new technique for acetabular reconstruction using modular implants fashioned with a new biomaterial, porous tantalum, which had specific properties favoring osteointegration.

Material and methods: These modular implants were fashioned so as to enable reconstruction of the acetabular cavity in cases with complex loss of bone stock. The design allows simultaneous biological incorporation and mechanical support with a press-fit hemispheric cup. These implants were used for 16 hips (16 patients, 12 women and 4 men, mean age 63.6 years, age range 34–86 years). These patients were followed for 31.9 months on average (range 24–39 months). The acetabular defects were Paprosky 2A (n=1), 2B ‘n=3), 2C (n=1), 3A (n=5), 3B (n=6). On average, these patients had undergone 2.8 cup replacements (1–9) on the same hip.

Results: The mean Harris hip score improved from 39.31 (range 33–52) preoperatively to 75.18 (range 52–92) at last follow-up. Preoperatively, the center of rotation of the prosthetic hip was situated a a mean horizontal distance of 18.6 mm (range −3 to 46 mm) and a mean vertical distance of 27.6 mm (range −16 to 52 mm) from the ideal center of rotation according to Ranawat. Postoperatively, the prosthetic center of rotation was situated at a mean horizontal distance of 10.5 mm (range 1–25 mm) and a mean vertical distance of 7.4 mm (range −15 to 25 mm) front the ideal center of rotation. None of the implants presented loosening or migration at last follow-up.

Discussion: At short-term follow-up, this modular system for acetabular reconstruction has provided good results for acetabular reconstruction which can accept a hemispheric cup alone and which would have required use of other reconstruction methods such as structural allografts, sustaining rings or other.

Conclusion: A longer follow-up will be needed to determine whether these good clinical and radiological results persist with time.

There has been a longstanding need for a structural biomaterial that can serve as a bone graft substitute or implant construct and is effective for fixation by bone ingrowth. A porous tantalum material was developed to address these issues. The purpose of this paper and presnetation is to describe the properties and 2 to 5 year clinical results of porous tantalum in various reconstructive orthopaedic procedures.

Porous tantalum has been used to manufacture primary and revision acetabular cups, acetabular augments, tibial and patella implants, patellar augments, structural devices for the treatment of osteonecrosis, and spinal fusion implants. Clinical follow-up includes: 2–5 year clinical and radiographic evaluation of: 414 monoblock cups in primary THA, 36 monoblock cups and 587 revision hemispheres used in revision THR, 16 hips revised with acetabular augments and revision hemispheres; 2 to 4 years for 101 tibial implants used in primary TKR and 69 patellas used in cementless TKR; 2–4 years for 11 patellar augments in salvage TKR, 1–5 years for 53 revision TKRs using knee spacers; 1–4 years for 91 osteone-crosis hip implants; and for 15 cervical fusion cases.

This innovative tantalum implant material with trabecular architecture possesses advantages in stiffness, friction coefficient, porosity, rate and extent of tissue ingrowth, and versatility in manufacturing of structural devices. It has been clinically validated in numerous and diverse reconstructive procedures.

Press-fit acetabular reconstructions have become the standard THA; however, controversies remain. The purpose of this study was to critically evaluate serial radiographs for initial cup stability, i.e. gaps and signs of periacetabular interface changes for a porous tantalum monoblock socket.

A multicenter study evaluating 574 primary THRs (542 patients) performed by 9 surgeons at 7 hospitals, all with a monoblock cup without screws. Analyses included clinical outcomes and detailed 2-year minimum radiographic evaluation by one independent observer (mean follow-up, 33 months).

Complications included 9 intra-operative acetabular fractures. Among the 123 cases excluded from radiographic evaluations: deceased (19), lost-to-follow-up (8), 7 early revisions (recurrent dislocations (6) and one trauma-related loosening), and sepsis (3). Patient demographics (414 hips): mean age 65 years (19–93); 58 percent females. Baseline radiographs revealed 113 zones in 85 hips (21 percent) with acetabular gaps; 36 in zone I, 72 in zone II, and 5 in zone III. Of these radiolucencies, 57 zones were 1 mm or less and 56 zones ranged from 2 to 5 mm. At last follow-up, 64 hips (75 percent) had complete gap fill-in, including 100 percent of gaps greater than 3 mm.

There were no socket migrations, no evidence of lysis, no revisions for loosening, and no complete periacetabular interface radiolucencies. The fill-in of preexisting OA cysts and gaps is attributed to adequate initial stability and osteointegration into the porous tantalum. These results suggest that a monoblock cup without screws is an attractive option in THA.

Reliable soft tissue attachment to prosthetic implants remains a great clinical challenge in adult reconstruction and oncology. Past efforts using tendon alone have been universally disappointing. With the introduction of trabecular metals, new possibilities present them selves in dealing with this problem. Using an established canine supraspinatus tendon model, reliable and physiologic soft tissue attachment to a trabecular metal prosthesis was achieved, with near normal strength and function. This suggests that this new genre of material can possibly provide better options in dealing with this difficult problem.

Direct attachment of tendon to an endoprothesis has applications throughout the field of orthopaedics. The purpose of this study was to devise a soft-tissue attachment device using tantalum foam metal which would allow for early soft tissue reconstruction strength and long term biologic in-growth fixation.

A foam metal tendon attachment prosthesis was designed. Using a validated tendon attachment model, twenty-three skeletally-mature canine supraspinatus tendons were sharply detached and then reattached to the greater tuberosity. Ultimate strength, stiffness and gross morphological changes were recorded immediately after surgery and at three and six weeks.

Tendon-implant strength as percent of normal rose from thirty-nine percent at surgery, to sixty-seven percent at three weeks, and ninety-nine percent at six weeks (standard deviations thirteen, nineteen, and eighteen percent). Stiffness of construct also approached normal tendon: forty-seven percent at surgery, sixty-two percent at three weeks, and ninety-four percent at six weeks (standard deviations seventy-seven, nineteen, and eighteen percent). Supraspinatus muscle volume decreased from ninety seven (percent of normal) at surgery, to seventy-nine percent at three weeks. By six weeks, the muscle had recovered to ninety percent of normal volume. Gross and histologic analysis revealed complete tendon in-growth and attachment to the prosthesis with the formation of Sharpey’s fibers

This study suggests that tendon attachment to a metallic endoprothesis is possible. Near normal physiologic strength and stiffness was achieved six weeks post surgery. Future study should ascertain the micro-anatomy of this attachment and delineate the mechanical conditions necessary for soft tissue in-growth.

Funding: Zimmer, Inc., Warsaw, IN

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We aimed to determine the optimal method of inserting a screw into polymethylmethacrylate (PMMA) cement to enhance fixation. We performed six groups of ten axial pull-out tests with two sizes of screw (3.5 and 4.5 mm AO cortical) and three methods of insertion. Screws were placed into 'fluid' PMMA, into 'solid' PMMA by drilling and tapping, or into 'curing' PMMA with quarter-revolution turns every 30 seconds until the PMMA had hardened. After full hardening, we measured the maximum load to failure for each screw-PMMA construct. We found no significant difference in the pull-out strengths between screw sizes or between screws placed in fluid or solid PMMA. Screws placed in curing PMMA were significantly weaker: the relative strengths of solid, fluid and curing groups were 100%, 97% and 71%, respectively. We recommend the use of either solid or fluid insertion according to the circumstances and the preference of the surgeon.

Between 1976 and 1988, 50 primary total knee arthroplasties were performed on 34 patients with psoriasis vulgaris. The skin lesions were graded for severity in all patients and the extent of affected body surface was mapped. All patients received peri-operative antibiotics. Only one deep infection, with Staphylococcus aureus, occurred 25 months after operation. The average length of follow-up was nearly four and a half years, being to a minimum of two years or until failure of the arthroplasty. There appears to be no increased risk of deep infection in patient with psoriasis vulgaris undergoing primary total knee arthroplasty.

We made a retrospective study of 55 primary total hip arthroplasties in 53 patients with a history of previous acetabular fracture. The mean follow-up was 7.5 years and the average age at fracture was 48.7 years. The incidence of radiographic femoral loosening (29.4%), symptomatic loosening (15.7%), and femoral revision (7.8%) were similar to those previously reported at 10 years for routine arthroplasties by Stauffer (1982). On the acetabular side, the incidence of radiographic loosening (52.9%), symptomatic loosening (27.5%), and revision (13.7%) were four to five times higher. We conclude that a history of prior acetabular fracture has a significant adverse impact on the long-term outcome of any subsequent total hip arthroplasty.