Rothman Institute team finds promise in metaphyseal fixation

Metaphyseal sleeves aid reconstruction of severe bone loss.

Matthew S. Austin

SAN DIEGO – At the 2011 meeting of the American Academy of Orthopaedic Surgeons, Matthew S. Austin, MD, discussed results of several studies on revision total knee arthroplasty (TKA) techniques. He reviewed outcomes of previous studies on traditional TKA methods, then presented results of a study conducted at the Rothman Institute using metaphyseal sleeves to achieve fixation and manage significant bone defects during revision TKA procedures.¹

Austin and his team reviewed several surgical approaches for dealing with severe bone loss in revision TKA, addressing bone loss with techniques such as allografts and augments, and later reviewing the use of metaphyseal sleeves.

Traditional revision techniques

Overall, short-term to mid-term outcomes are reasonable for traditional techniques, but larger defects make reliable reconstitution more difficult with these historic approaches.

CANCELLOUS ALLOGRAFT

Impaction grafting reconstructs large defects. Although mid-term results for impaction grafting are promising, Austin determined that “it is a technically demanding procedure and quite time consuming.” In one study of 42 patients by Lotke, 14% experienced complications postoperatively.²

BULK ALLOGRAFT

Studies to examine the effectiveness of bulk allograft in restoring bone stock were also reviewed. Bulk allograft potentially restores bone stock, with studies by Ghazavi noting mid-term results of up to a 77% success rate.³ Furthermore, Engh’s study showed no evidence of collapse at a 50-month follow-up when used in conjunction with a long-stemmed, cemented component.⁴ However, drawbacks include the potential for resorption, collapse and the need for protected weight-bearing.

STRUCTURAL ALLOGRAFT

Structural allograft results were also reviewed. Structural allograft can bridge larger gaps, potentially restore bone stock and provide good support for the prosthesis. In a report of 52 knees, outcomes at 10 years were 72% survivorship rate, 8% infection rate and 8% graft-resorption rate. Disadvantages include time and technical demands, allograft nonunion, infection and risk of disease transmission (Figure 1).⁵

METAL AUGMENTS

Traditional metal augments provide generally acceptable outcomes as well. Patel and colleagues showed that metal augments substituted for deficient bone stock, with outcomes at 11 years showing a 92% survival rate for small defects up to 2 cm. However, they do not restore bone stock, they require bone removal and, therefore, are inadequate for large defects.⁶

Metaphyseal fixation

New metaphyseal fixation procedures have emerged to fill severe defects, including Trabecular Metal cones and tibial and femoral sleeves. Early study results are positive, but long-term follow-up is needed to garner better evidence.

TRABECULAR METAL

Several studies have recently demonstrated short-term evidence of osseointegration and provision of a good surface for cement interdigitation. Surgeons have reported no signs of loosening at early follow-up.^7-8 Using trabecular metal, however, may require removal of additional bone, and there is no true system for implantation at this time, according to the Rothman team.

METAPHYSEAL SLEEVES

The Rothman Institute study on metaphyseal sleeves spanned 42 months, from January 2007 to June 2010, during which the group performed 337 knee revisions. Eighty-three patients (86 knees) received the Total Condylar 3 (TC3; DePuy Orthopaedics, Inc.) prosthesis with titanium metaphyseal sleeves, while 14 patients (15 knees) received S-ROM Noiles hinged prostheses (DePuy Orthopaedics, Inc.). In total, surgeons implanted 100 tibial sleeves and 46 femoral sleeves (Figure 2).

“Structural allograft can bridge larger gaps, potentially restore bone stock and provide good support for the prosthesis.”

— Matthew S. Austin, MD

Forty-four patients completed at least 1 year of clinical follow-up, with the average being 2.4 years. Mean age was 65.5 years (range: 42 to 81 years) with 16 males and 28 females. Topping the list of indications for revision were aseptic loosening (43%) and second-stage reimplantation (27%). Using the Anderson Orthopaedic Research Institute (AORI) classification, Austin’s group categorized the majority of defects as type 2B and type 3 (Figure 3).

Three patients required reoperation, one for aseptic loosening and two for re-infection after reimplantation as part of a two-stage procedure.

“Metaphyseal sleeves fill the defect, achieve axial and rotational stability, allow for rotational freedom, and include a wide range of sizes. Our short-term results show that tibial and femoral metaphyseal sleeves are a viable alternative to traditional revision TKA techniques if severe bone loss exists,” Austin stated.

Austin cautioned that these results are preliminary, and mid- to long-term follow-up is necessary.

Conclusions

In summary, each revision TKA method has its benefits when attempting to repair bone defects and address stability. However, the techniques for reconstruction of severe bone loss are still evolving.

Metaphyseal fixation provides promising results and short-term follow-up in addition to having a successful track record with the S-ROM Hinge since 1985.

“The findings in our study are encouraging. Metaphyseal sleeves allow reconstruction of the knee in severe bone loss by allowing rigid initial fixation and proper alignment,” Austin said.

References

1. Jafari SM, Coyle C, Huang R, et al. Revision total knee arthroplasty using metaphyseal sleeves at short-term follow-up. Presented at: the American Academy of Orthopaedic Surgeons 2011 Annual Meeting. February 15-19, 2011. San Diego.
2. Lotke PA, Carolan GF, Prui N. Impaction grafting for bone defects in revision total knee arthroplasty. Clin Orthop Relat Res. 2006;446:99-103.
3. Ghazavi MT, Stockley I, Yee G, et al. Reconstruction of massive bone defects with allograft in revision total knee arthroplasty. J Bone Joint Surg Am. 1997;79:17-25.
4. Engh GA, Herzwurm PJ, Parks NL. Treatment of major defects of bone with bulk allografts and stemmed components during total knee arthroplasty. J Bone Joint Surg Am. 1997;79:1030-1039.
5. Clatworthy MG, Ballance J, Brick GW, et al. The use of structural allograft for uncontained defects in revision total knee arthroplasty. J Bone Joint Surg Am. 2001;83: 404-411.
6. Patel JV, Masonis JL, Guerin J, et al. The fate of augments to treat type-2 bone defects in revision total knee arthroplasty. J Bone Joint Surg Br. 2004;86 B:195-199.
7. Meneghini RM, Lewallen DG, Hanssen AD. Use of porous tantalum metaphyseal cones for severe tibial bone loss during revision total knee arthroplasty. J Bone Joint Surg Am. 2008;90:78-84.
8. Long WJ, Scuderi GR. Porous tantalum cones for large metaphyseal tibial defects in revision total knee arthroplasty. J Arthroplasty. 2009;24(7):1086-1092.

Matthew S. Austin, MD, has a direct financial interest in Trabecular Metal Cones, and he is a paid consultant for Zimmer, Inc. He also receives research support from DePuy Orthopaedics, Inc.