摘要:

Bone remodeling around an endoprostheses is dependent on the site of healing of the bone to the bone ingrowth stem and to the stiffness of the stem. The healing associated with the bone ingrowth pattern is characterized by the spot weld formation as described by Engh for fixation in the diaphysis. With healing in the metaphysis the pattern is one which we have termed the “buttress pattern of healing.” On x-ray film this appears as a medial and lateral condensation of bone that directs the load into the diaphyseal cortices. When the implant is stable, the endosteal healing progresses along the entire length of the stem moving from proximal to distal. The bone demonstrates less stress shielding if the bone is loaded parallel to its grain rather than across the grain. Implant retrieval demonstrates a neocortex of bone that forms along the length of the stem. If the implant is stable, the neocortex forms adjacent to the metal. With motion of the stem, the neocortex forms at the periphery of the motion and a radiolucent line is evident on the film. On implant retrieval all bone around a hip stem is seen to be osteoporotic. In revision bone the same patterns of healing are seen. The initial stability and healing of the implant is more dependent on the structure of the bone than the cellular function of the bone because this cellular function is much the same regardless of the amount of osteolysis.

ISSN:0885-9698    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

This article describes the authors' approach to using extensively porous coated femoral components without cement in revision hip arthroplasty. Topics covered include preoperative evaluation, surgical planning, surgical approaches, implant removal, reimplantation, perioperative complications, and postoperative rehabilitation. The article stresses the importance of the quality of acetabular and femoral bone stock in planning surgery and of the postoperative rehabilitation program to achieve durable implant fixation.

ISSN:0885-9698    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Cortical strut allografting is indicated in patients with femoral deficiencies, primarily in revision hip arthroplasties. Most defects are caused by osteolysis, which may be localized or global. Healing of struts is predictable in 96.6% of cases. Clinical hip scores are also improved by more than 30 points, despite the severity of bone defects.

ISSN:0885-9698    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

In revision total hip replacement surgery, treatment of the expanded femoral medullary canal is a challenging problem. Large volumes of cement, or massive custom components frequently fail and result in even larger defects and thinning of the remaining cortices.In this article, seventeen patients with intramedullary structural grafts were followed for an average of 50 months with a range of 8 months to 8 years, three months. There were 16 allografts and one iliac crest autograft. Nine cancellous metaphyseal grafts were shaped as a truncated cone and were impacted within the host metaphysis. The femoral component was then cemented within the graft. I now prefer to use an allograft proximal tibia and to protect the host femur with circlage cables. The ZTT metaphyseal unit of the Joint Medical Stem (Stamford, CT) is cemented to the graft and the fluted stem is used in the host femur without cement.Seven smaller allograft femurs were impacted within the expanded diaphyseal canal of the host femur and new femoral components were cemented within these grafts. I now prefer to machine the outer diameter of a smaller femur to just fit within the host medullary canal but leave an abrupt shelf at the host graft junction. The distal allograft is pressfit within the host but the butt joint resists further subsidence. The host femur is protected by a circlage cable. All nine metaphyseal grafts united. Five of the smaller allograft femurs united, but two did not and both subsided. The two grafts that did not unite were technical failures as a butt joint was not used and fixation was achieved only by a pressfit.

ISSN:0885-9698    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Loosening of acetabular components causes loss of bone stock secondary to polyethylene wear. There are several types of bone loss that give certain radiographic presentations. Each bone loss type requires a specific type of reconstruction employing different bone grafting techniques. Superior migration of the acetabular component greater than 2-3 cm in combination with severe posterior rim loss manifested as severe ischial lysis on x-ray film indicates a need for support allograft to achieve stability since greater than 30% of the cup will not be supported by host bone.If the inner table of the medial acetabulum is violated as well, then over 60% of the component is not in contact with host bone. Biologic fixation of the cup is unlikely in these instances and a whole acetabular graft with cemented component is needed. Of the 316 acetabular revisions performed from 1982—1991 with a mean follow-up of 5.1 years, 69 required support allograft or whole acetabular grafts. In the remaining cases, only cancellous bone was used to fill defects since the rim was supportive. There was less than 2 cm of superior migration of the component and only minimal ischial and medial bone loss. A maximum of 30% of the porous surface of the cup was not in contact with host bone.

ISSN:0885-9698    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Revision surgery following total hip replacement (THR) has become increasingly frequent over the past decade. Clinical success with revision THR has been inferior to primary surgery in both cemented and cementless reconstructions. Significant improvements in the clinical success of cemented revision THR have been accomplished using modern techniques and implants. Although cementless revision has become increasingly popular, an 80% to 90% success rate can be achieved with cemented revision THRs at medium-term followup. In this article, the authors present preoperative evaluation, surgical techniques of cemented acetabular and femoral revisions, and clinical results of several large series.

ISSN:0885-9698    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Treatment of an infected total hip prosthesis can be a complex and lengthy endeavor for the joint arthroplasty surgeon. Initially the surgeon's objective is to identify and eradicate the infection by the debridement of all prosthetic materials, all nonviable soft tissues and any poorly vascularized structures including bone. The removal of all cement and metal is essential, as an increased rate of recurrent infection has been correlated with failure to remove those materials. The purpose of this article is to describe the surgical treatment including component removal and reimplantation techniques necessary to obtain the ultimate desired outcome of a functional, sterile hip prosthesis.

ISSN:0885-9698    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Intramedullary instruments provide a highly reliable landmark for varus-valgus alignment of the components in total knee arthroplasty while rotational alignment of the femoral component can be adjusted reliably by sighting the femoral epicondyles. Correct positioning of the joint line is essential to achieve stable ligament tension in flexion and extension. Varying thicknesses of femoral and tibial components allow the surgeon to place the joint line correctly and restore stability and ligament balance in virtually all knees without resorting to hinges or highly constrained implants.Bone deficiency can be managed with allograft if rigid fixation of the implants can be achieved. Smooth stems that fit tightly in the medullary canal of the femur and tibia give excellent support for the articular portion of the implant, and allow cement less fixation and morselized allograft reconstruction of major bone defects.

ISSN:0885-9698    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The key to technical success in revision total knee replacement lies in making the right choices at the time of trial reduction. This will enable the use of devices that are not fully constrained but in which the soft tissue stabilizers around the knee participate in the functional stability of the knee. This article presents two case studies that review the surgical technique of recutting the bone and trial reduction.

ISSN:0885-9698    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The importance of preventing infection in total knee arthroplasty (TKA), as well as effectively treating the infected arthroplasty, is readily apparent. Preventing infection after TKA involves recognizing the preoperative, intraoperative and postoperative variables that predispose to infection. Successful treatment of the infected TKA involves selection of the appropriate treatment modality. While acute infections may be eradicated by debridement alone, chronic infections will require prosthesis removal and further treatment (either reimplantation, or arthrodesis in a clean bed). Selection of the appropriate treatment is based on both clinical and radiographic considerations.

ISSN:0885-9698    

出版商:OVID    

年代:1993

数据来源: OVID