Aims

Modular dual mobility (MDM) acetabular components are often used with the aim of reducing the risk of dislocation in revision total hip arthroplasty (THA). There is, however, little information in the literature about its use in this context. The aim of this study, therefore, was to evaluate the outcomes in a cohort of patients in whom MDM components were used at revision THA, with a mean follow-up of more than five years.

Aims

The aim of this study was to examine the results of the acetabular distraction technique in achieving implantation of a stable construct, obtaining biological fixation, and producing healing of chronic pelvic discontinuity at revision total hip arthroplasty.

Using the Mayo Clinic definition (>62mm in women and >66mm in men), the “jumbo acetabular component” is the most successful method for acetabular revisions now, even in hips with severe bone loss. There are numerous advantages: surface contact is maximised; weight-bearing is distributed over a large area of the pelvis; the need for bone grafting is reduced; and usually, hip center of rotation is restored. The possible disadvantages of jumbo cups include: may not restore bone stock; may ream away posterior column or wall; screw fixation required; the possibility of limited bone ingrowth and late failure; and a high rate of dislocation due to acetabular size:femoral head ratio. The techniques for a successful jumbo revision acetabular component involve: sizing-“reaming” of the acetabulum, careful impaction to achieve a “press-fit”, and multiple screw fixation. We recommend placement of an ischial screw in addition to dome and posterior column screw fixation. Cancellous allograft is used for any cavitary defects. The contra-indications for a jumbo acetabular cup are: pelvic dissociation; inability to get a rim fit; and inability to get screw fixation. If stability cannot be achieved with the jumbo cup alone, then use of augment(s), bulk allograft, or cup-cage construct should be considered. Using titanium fiber-metal mesh components, we reported the 15-year survival of 129 revisions. There was 3% revision for deep infection and only 3% revision for aseptic loosening. There were 13 reoperations for other reasons: wear, lysis, dislocation, femoral loosening, and femoral fracture fixation. The survival was 97.3% at 10 years, but it dropped to 82.8% at 15 years. Late loosening of this fiber metal mesh component is likely related to polyethylene wear and loss of fixation. Dislocation is the most common complication of jumbo acetabular revisions, approximately 10%, and these are multifactorial in etiology and often require revision. Based on our experience, we now recommend use of an acetabular component with an enhanced porous coating (tantalum), highly crosslinked polyethylene, and large femoral heads or dual mobility for all jumbo revisions

Total hip arthroplasty continues to be one of the most effective procedures. Aseptic loosening compromises the long term outcome of this otherwise successful procedure. Large hemispherical cups may be used during revision surgery for patients with severe bone loss. Acetabular revision with cementless components has been remarkably successful with some series reporting no revisions for aseptic loosening at an average follow-up of 13.9 years. Another study on 186 patients (196 hips) receiving jumbo acetabular components, noted a survivorship of 98% at 4 years and 96% at 16 years. Cementless acetabular revision is now feasible for a wide range of revision situations, including some cases of pelvic discontinuity. The Paprosky classification is useful in predicting the reconstructive technique that will be required. Type I and many Type II defects may be reconstructed with standard cementless components. Many Type II and Type III defects, which involve the loss of additional structural bone, can be reconstructed with a jumbo cup. A jumbo cup is defined by Whaley et al. as a component that is >61 mm in women and >65 mm in men, a definition that is based on a shell that is >10 mm greater than the average diameter cup implanted in women and men. The jumbo cup has the advantage of an increased contact area between host bone and cup which maximises the surface area for ingrowth or ongrowth. The increased area of contact also prevents cup migration by allowing for force dissipation over a large area. Use of a jumbo cup may also decrease the need to use bone graft. In contrast to positioning the cup in the so-called high hip center, a jumbo cup can help to restore the hip center of rotation. The disadvantages of this technique are that host bone may have to be removed to implant the cup, that bone stock is not restored by the reconstruction, and that hemispherical cups have limited applicability in situations of oblong bone stock deficiency. Jumbo acetabular components can be used in combination with both structural and cancellous bone graft. In these cases, the cementless cup must achieve adequate contact with host bone in order to allow bone ingrowth to occur

The ‘jumbo’ acetabular component is now commonly used in acetabular revision surgery where there is extensive bone loss. It offers high surface contact, permits weight bearing over a large area of the pelvis, the need for bone grafting is reduced and it is usually possible to restore centre of rotation of the hip. Disadvantages of its use include a technique in which bone structure may not be restored, a risk of excessive posterior bone loss during reaming, an obligation to employ screw fixation, limited bone ingrowth with late failure and high hip centre, leading to increased risk of dislocation. Contraindications include unaddressed pelvic dissociation, inability to implant the component with a rim fit, and an inability to achieve screw fixation. Use in acetabulae with < 50% bone stock has also been questioned. Published results have been encouraging in the first decade, with late failures predominantly because of polyethylene wear and aseptic loosening. Dislocation is the most common complication of jumbo acetabular revisions, with an incidence of approximately 10%, and often mandates revision. Based on published results, a hemispherical component with an enhanced porous coating, highly cross-linked polyethylene, and a large femoral head appears to represent the optimum tribology for jumbo acetabular revisions.

Cite this article: Bone Joint J 2016;98-B(1 Suppl A):64–7.

Using the Mayo Clinic definition (>62mm in women and >66mm in men), the “jumbo acetabular component” is the most commonly used method for acetabular revisions now. There are numerous advantages: surface contact is maximised; weight-bearing is distributed over a large area of the pelvis; the need for bone grafting is reduced; and usually, hip center of rotation is restored. The possible disadvantages, or caveats, of jumbo cups include: may not restore bone stock; may ream away posterior column or wall; screw fixation required; the possibility of limited bone ingrowth and late failure; and a high rate of dislocation due to acetabular size:femoral head ratio. The techniques for a successful jumbo revision acetabular component involve: sizing-“reaming” of the acetabulum, careful impaction to achieve a “press-fit”, and multiple screw fixation. We recommend placement of an ischial screw in addition to dome and posterior column screw fixation. Cancellous allograft is used for any cavitary defects. The contraindications for a jumbo acetabular cup are: pelvic dissociation; inability to get a rim fit; inability to get screw fixation; and the presence of <50% living host bone. If stability cannot be achieved with the jumbo cup alone, then use of augment(s), bulk allograft, or cup-cage construct should be considered. Our results with the jumbo acetabular cups in revision arthroplasty have been reported. Using predominantly titanium fiber-metal mesh components, we reported the 15-year survival of 129 revisions. There was 3% revision for deep infection and only 3% revision for aseptic loosening. There were 13 reoperations for other reasons: wear, lysis, dislocation, femoral loosening, and femoral fracture fixation. The survival was 97.3% at 10 years, but it dropped to 82.8% at 15 years. Late loosening of this fiber metal mesh component is likely related to polyethylene wear and loss of fixation. Dislocation is the most common complication of jumbo acetabular revisions, approximately 10%, and these are multifactorial in etiology and often require revision. Based on our experience, we now recommend use of an acetabular component with an enhanced porous coating (tantalum), highly cross-linked polyethylene, and large femoral heads for all jumbo revisions

Migration of the acetabular component may give rise to oval-shaped bone defects in the acetabulum. The oblong implant is designed to fill these defects and achieve a stable cementless anchorage with no significant bone loss. We prospectively reviewed 133 oblong long oblique revision components at a mean follow-up of 9.74 years (0.6 to 14). All had been used in revisions for defects of type IIB to IIIB according to Paprosky. Aseptic loosening was the reason for revision in 11 cases (8.3%) and deep infection in seven (5.3%). The probability of implant survival over a 12-year follow-up estimated by the Kaplan-Meier method gave a survival rate of 0.85% respectively 0.90% when deep infection was excluded as the endpoint.

Our study supports the use of these components in defects from IIB to IIIA. The main precondition for success is direct contact of more than half of the surface of the implant with the host acetabular bone.