Orthopedics

Shell Retention With a Cemented Acetabular Liner

John J. Callaghan, MD; Steve S. Liu, MD; Nathan M. Schularick, BA

Abstract

The authors reviewed the indications, technique, and results of cementing an acetabular liner into a well-fixed cementless acetabular shell. Indications for this procedure include a worn acetabular liner in a well-fixed cementless acetabular shell as well as an unstable total hip construct where the shell is secured. To perform such a procedure, an adequate shell diameter is necessary to accept an acetabular liner that will enable 2 mm of cement mantle around it. If the shell has screw holes, there is no need to score the acetabular shell, but otherwise the acetabular shell must be scored to a 1-mm depth in a spiderweb configuration. As for the acetabular liner, it too must be scored to a 1-mm depth in a spiderweb configuration (which enhances torsional stability) as well as a circular configuration to provide optimal lever-out strength. We have evaluated 31 constrained liners and 30 nonconstrained liners with this preparation. The failure rate in the constrained liner series was 6%, and no failures occurred in the nonconstrained series. One dislocation occurred in the nonconstrained series where patients were typically placed in a brace or cast for 6 weeks. This option should be considered in cases with worn-through acetabular liners for unstable configurations when the acetabular shell is well fixed and is of adequate diameter to accept such a construct.

Cementless acetabular components have been used for 20 years. Long-term follow-up has demonstrated excellent fixation of these components1; however, acetabular liner wear has been a significant long-term problem related to inadequate capturing mechanisms and gamma-irradiated-in-air polyethylene. This has left us with the clinical scenario where there is an intact well-fixed cementless acetabular component with the need for revision because of acetabular liner wear, instability, or both. Hence, the appropriate indication for cementing a new liner into an existing shell is when component fixation is secure, the capturing mechanism is damaged or inadequate for the polyethylene liner, and the shell diameter is large enough to accept a 28- or preferably 32- or 36-mm femoral head. Contraindications include a loose shell or osteolysis surrounding the shell potentially diminishing its long-term stability. Cases are contraindicated where the shell diameter or thickness prevents either of the following: 1) insertion of a liner with adequate thickness of polyethylene, or 2) allowance of a 1- to 2-mm cement mantle around the liner.

In our mechanical study of optimal liner shell preparation for cementing the liner into the shell, a number of technical details were discovered.2 If shells had screw holes, no further preparation of the shell was necessary. For optimal liner fixation, the liner needed a spiderweb or tic-tac-toe pattern 1-mm in thickness scored into the backside of the polyethylene to provide adequate torsional stability. In addition scoring the liner in a circular manner was necessary for lever-out stability. A 2-mm cement mantle was adequate for fixation. Failures always occurred between the cement and the liner, not between the cement and the shell. The lever-out and torsional stability of these configurations were stronger than those reported for modern day shell liner torsional and lever-out stability.

We have thoroughly evaluated a series where we cemented a constrained liner into a secure acetabular shell.3 At average 3.9-year follow-up of 31 cases, only 2 (6%) had failed. One failed due to leaving a liner proud (when the outer lip of the liner is not flush with the rim of the shell) and the other during a patient’s grand mal seizure. Both were successfully revised by cementing another liner into the shell.

We have also begun to evaluate a series of 30 acetabular components (nonconstrained) cemented into secure cementless acetabular shells.…

Abstract

The authors reviewed the indications, technique, and results of cementing an acetabular liner into a well-fixed cementless acetabular shell. Indications for this procedure include a worn acetabular liner in a well-fixed cementless acetabular shell as well as an unstable total hip construct where the shell is secured. To perform such a procedure, an adequate shell diameter is necessary to accept an acetabular liner that will enable 2 mm of cement mantle around it. If the shell has screw holes, there is no need to score the acetabular shell, but otherwise the acetabular shell must be scored to a 1-mm depth in a spiderweb configuration. As for the acetabular liner, it too must be scored to a 1-mm depth in a spiderweb configuration (which enhances torsional stability) as well as a circular configuration to provide optimal lever-out strength. We have evaluated 31 constrained liners and 30 nonconstrained liners with this preparation. The failure rate in the constrained liner series was 6%, and no failures occurred in the nonconstrained series. One dislocation occurred in the nonconstrained series where patients were typically placed in a brace or cast for 6 weeks. This option should be considered in cases with worn-through acetabular liners for unstable configurations when the acetabular shell is well fixed and is of adequate diameter to accept such a construct.

Cementless acetabular components have been used for 20 years. Long-term follow-up has demonstrated excellent fixation of these components1; however, acetabular liner wear has been a significant long-term problem related to inadequate capturing mechanisms and gamma-irradiated-in-air polyethylene. This has left us with the clinical scenario where there is an intact well-fixed cementless acetabular component with the need for revision because of acetabular liner wear, instability, or both. Hence, the appropriate indication for cementing a new liner into an existing shell is when component fixation is secure, the capturing mechanism is damaged or inadequate for the polyethylene liner, and the shell diameter is large enough to accept a 28- or preferably 32- or 36-mm femoral head. Contraindications include a loose shell or osteolysis surrounding the shell potentially diminishing its long-term stability. Cases are contraindicated where the shell diameter or thickness prevents either of the following: 1) insertion of a liner with adequate thickness of polyethylene, or 2) allowance of a 1- to 2-mm cement mantle around the liner.

Surgical Technique

In our mechanical study of optimal liner shell preparation for cementing the liner into the shell, a number of technical details were discovered.2 If shells had screw holes, no further preparation of the shell was necessary. For optimal liner fixation, the liner needed a spiderweb or tic-tac-toe pattern 1-mm in thickness scored into the backside of the polyethylene to provide adequate torsional stability. In addition scoring the liner in a circular manner was necessary for lever-out stability. A 2-mm cement mantle was adequate for fixation. Failures always occurred between the cement and the liner, not between the cement and the shell. The lever-out and torsional stability of these configurations were stronger than those reported for modern day shell liner torsional and lever-out stability.

Results

We have thoroughly evaluated a series where we cemented a constrained liner into a secure acetabular shell.3 At average 3.9-year follow-up of 31 cases, only 2 (6%) had failed. One failed due to leaving a liner proud (when the outer lip of the liner is not flush with the rim of the shell) and the other during a patient’s grand mal seizure. Both were successfully revised by cementing another liner into the shell.

We have also begun to evaluate a series of 30 acetabular components (nonconstrained) cemented into secure cementless acetabular shells. At minimum 2-year follow-up of 24 components, 2 have been revised for wear-through of the cemented polyethylene. In addition, there was one case of instability. Otherwise, the patients continued to function well at minimum 2-year follow-up (Figure).

Figure A: A Harris Galante I porous shell Figure B: A Harris Galante I porous shell

Figure: Preoperative (A) and 6-year follow-up (B) radiographs of a Harris Galante I porous shell (Zimmer, Warsaw, Indiana) with wear-through of the gamma-irradiated-in-air polyethylene liner, which was treated by scoring the backside of a crosslinked polyethylene liner and cementing it into the secure shell.

Discussion

Cementing a liner into a secure shell was first reported by Heck and Murray4 where they cemented a liner into the metal shell of a McKee-Farrar component (Howmedica, Limerick, Ireland). Due to the large number of cases using cementless acetabular fixation with first generation locking mechanisms and gamma-irradiated-in-air polyethylene, a large number of hips need or potentially need revision for acetabular liner wear and instability with fixed cementless shells. Beaule et al5 have reported results using this technique and demonstrated excellent fixation of the cemented liners into the shell but had a 22% dislocation rate. In our series where we used both constrained and nonconstrained liners, we have demonstrated a minimal problem with postoperative instability. Two reasons for this are that we (other than in the initial few years) used a relatively large femoral head in the cases of nonconstrained liners. In addition, we would brace or even apply a half hip spica cast for 6 weeks. Optimal preparation of the backside of the acetabular liner and assuring a 2-mm cement mantle thickness without cementing the liner proud can provide excellent durability for this difficult problem.

References

  1. Gaffey JL, Callaghan JJ, Pedersen DR, et al. Cementless acetabular fixation at fifteen years. A comparison with the same surgeon’s results following acetabular fixation with cement. J Bone Joint Surg Am. 2004; 86(2):257-261.
  2. Haft GF, Heiner AD, Dorr LD, Brown TD, Callaghan JJ. A biomechanical analysis of polyethylene liner cementation into a fixed metal acetabular shell. J Bone Joint Surg Am. 2003; 85(6):1100-1110.
  3. Callaghan JJ, Parvizi J, Novak CC, et al. A constrained liner cemented into a secure cementless acetabular shell. J Bone Joint Surg Am. 2004; 86(10):2206-2211.
  4. Heck DA, Murray DG. In vivo construction of a metal-backed, high-molecularweight polyethylene cup during McKee-Farrar revision total joint arthroplasty. A case report. J Arthroplasty. 1986; 1(3):203-206.
  5. Beaulé PE, Ebramzadeh E, LeDuff M, Prasad R, Amstutz HC. Cementing a liner into a stable cementless acetabular shell: the double-socket technique. J Bone Joint Surg Am. 2004; 86(5):929-934.

Authors

Drs Callaghan and Liu and Mr Schularick are from the University of Iowa, and Dr Callaghan is also from the VA Medical Center, Iowa City, Iowa.

Dr Callaghan is a consultant for and receives royalties from DePuy. Drs Liu and Schularick have no relevant financial relationships to disclose.

Presented at Current Concepts in Joint Replacement 2008 Winter Meeting; December 10-13, 2008; Orlando, Florida.

Correspondence should be addressed to: John J. Callaghan, MD, 200 Hawkins Dr, UIHC, 01029 JPP, Iowa City, IA 52242.

DOI: 10.3928/01477447-20090728-17

10.3928/01477447-20090728-17

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