Revision Acetabulum Treatment Options: The Use of Jumbo Cups

Michael Gross, M.D., FRCSC
Halifax, NS

Revision hip surgery presents the surgeon with many challenges. The goals of revision hip surgery are to: 1) restore normal hip function in terms of stability and kinematics, and 2) preserve or enhance pelvic bone stock while obtaining secure fixation of components.

Large osseous defects are common in the acetabulum in hip revision surgery. The most common cause is osteolysis secondary to polyethylene wear. The next most common causes are congenital hip dysplasia or surgical loss secondary to multiple revisions.

The bone loss can be classified, such as by the AAOS, but usually the superior lip of the acetabulum is the first to go, followed by medial wall. The anterior or posterior column deficiencies are dependant on the previous approach to the hip and the amount of bone lost to the initial reaming and subsequent loosening. The medial wall is often broached, particularly by osteolytic processes secondary to a cup with open holes medially. However the osteolytic revision acetabulum often has large cancellous bone defects where the granulation material has extended from the backside of the cup.

The use of a jumbo cup is meant to overcome some of these reconstructive challenges by accepting the osseous defects and placing a large cup in situ, depending on the remaining bone to provide osseous stabilization of the cup by host bone in growth. Screws are mostly used to anchor the cup to the host bone. The advantages of the increased cup size are: 1) avoiding structural bone graft or reconstruction, and 2) allowing for the use of larger femoral head sizes with thick liners. The larger femoral heads may contribute to a decreased dislocation rate and better hip kinematics.

The issue with jumbo cups is whether or not they actually achieve osseous integration and whether the long-term outcomes are equivalent or better than those with osseous defect reconstruction with bone and smaller cups.

Literature Review
There is very little literature on the outcome of jumbo cups in revision hip surgery. Many papers initially reviewed case series of patients undergoing hip revision surgery where larger cups were used. One example is by Whaley et al7. They reviewed at five years the results of a large uncemented hemispherical acetabular component where the outside diameters were > or = to 66 mm in men and 62 mm in women. Particulate bone graft was used in 54 out of 89 hips and bulk allograft in nine. Four acetabular cups had been revised and two sockets had signs of definitive radiological loosening.

Obenaus et al found similar outcomes in their smaller series5. Their retrospective study of 60 acetabular revisions, with bone graft in 17 cases, demonstrated early migration in six cases, and one loosening requiring revision. They stated that the early migrators stabilized after two years. Their conclusions were that high friction coefficients in the cups offered sufficient stability even in severe cases.

The best evidence of press-fit cup stability as measured by radiostereometric analysis comes from Nivbrant et al.4 The migration of 60 press-fit cups with screws was evaluated with RSA for two years after revision for aseptic loosening. The mean proximal migration of the cup centre was up to 0.36 mm, whereas migration in other directions reached a level at 0.3 to 0.4 mm after six months. The factors that influenced motions were cup size, use of bone grafts, and position of the cup centre in the vertical and horizontal directions. Overall, the migration was higher than that seen in similar cups used in primary surgery.

Further information using RSA techniques comes from Ornstein et al who reported on a five-year follow-up of 17 patients6. Of the 17 patients available out of the initial cohort of 21 patients, five cases showed radiographic signs of allograft resorption and high rates of socket migration. Of the six cases that had migrated between 1.5 and two years, three stabilized and three were among those with signs of radiographic loosening.

Individual surgeon experiences with jumbo cups as reported in the literature include Gustke3. He used jumbo cups in 166 (29%) of patients, placing 19% in a high hip centre. One jumbo cup was revised for aseptic loosening.

Similarly the Asian experience is reported by Fan et al.2 In their review of 47 patients at four years, only three implant failures requiring re-revision were identified.

Other forms of jumbo cups, the so called "bi-lobed or oblong" cups have been used.

Abeyta et al1 retrospectively reviewed their experience with 25 consecutive acetabular reconstructions, where the defects were type III as per the AAOS classification system. Their 11-year follow-up on 14 patients with 15 hips demonstrated three obvious failures, and one implant with circumferential radio-lucency.

Engh et al reviewed their experience with the bi-lobed cup in 41 hips in 38 patients. After a four to eight-year follow-up, they found a 24% failure rate. Their recommendation was that the medial wall of the acetabulum should be intact if the failed component had migrated more than two centimetres.

Conclusions
The limited literature review suggests that migration followed by stabilization can occur with jumbo cups that are initially well fixed. There are also strong suggestions that bone grafting can enhance this stability. RSA measurements support a stable implant at five years but the paper by Ornstein is worrying. It appears that structural allografts are more prone to failure and therefore prejudice the outcome of the cup itself.

High friction jumbo cups can be stable, even in severe cases, and new metal designs offer hope for improvement. RSA studies should be done for each type of new metal preparation as these new cups are introduced to the market. It would be better for the orthopaedic community to know how well each jumbo cup performs at two years before the cup is widely used.

Oblong or bi-lobed cups do not seem to have the same results as jumbo cups, and there is no obvious compelling reason to continue using them if the jumbo cups continue to perform better.

None of the papers reviewed has addressed the issue of hip stability and tribology. The case that good long-term fixation can be achieved is supported by the literature in the mid-term but not in the long-term. If the long-term results continue to be satisfactory, then it may be that, in addition, the use of larger heads with improved bearing surfaces will reduce the dislocation rate and decrease production of pathological wear.

Overall, my own practice is to use large cups that engage some part of the patient's remaining host bone with a high friction fit. Bone defects are grafted with allograft cancellous bone. Thirty-two millimetre femoral heads seem to produce an acceptably stable hip construct with a low dislocation rate.

Demand for revision hip surgery may diminish if the improvements in tribology result in decreased wear and decreased loosening in the future. It is my impression that the rate of femoral loosening is decreasing with improved cement techniques and more stable non-cemented components. If the issue of wear can be addressed in primary hip arthroplasty, then revision surgeons may see less work in the future!

References

  1. Abeyta P.N., N. R., Janku G.V., Murray W.R., Kim H.T. (2008). "Reconstruction of major segmental acetabular defects with an oblong-shaped cementless prosthesis: a long term study." J Arthroplasty 23(2)(Feb): 247-53.          
  2. Fan C.Y., C. W., Lee O.K., Huang C.K., Chiang C.C., Chen T.H. (2008). "Acetabular revisions arthroplasty using jumbo cups: an experience in Asia." Arch Orthop Trauma Surg. 128 (8)(Aug): 809-13.           
  3. Gustke K.A., G. (2004). "Jumbo cup or high hip center: is bigger better?" J Arthroplasty 19(4 Suppl 1 )(Jun): 120-3.           
  4. Nivbrant B., K. J., Onsten I., Carlsson A., Snorrason F. (1996). "Migration of porous press-fit cups in hip revision arthroplasty. A radiosterometric 2-year follow-up study of 60 hips." J Arthroplasty 11 (4)(June): 390-6.       
  5. Obenaus C., W. H., Girtler R., Huber M., Schwagerl W. (2003). "Extra-large press-fit cups without screws for acetabular revision." J Arthroplasty 18(3)(Apr): 271-7.         
  6. Ornstein E., F. H., Johnsson R., Stefansdottir A., Sundberg M., Tagil M. (2006). "Five year follow up of socket movements and loosening after revision with impacted morselized allograft bone and cement: a radiostereometric and radiographic analysis." J Arthroplasty 21(7)(Oct): 975-84.        
  7. Whaley A.L., B. D., Harmsen W.S. (2001). "Extra-Large Uncemented Hemispherical Acetabular compinents for revision total hip arthroplasty." J Bone Joint Surg Am 83-A(Sept): 1352-7.         

 

 

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