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Ask the Experts: Patient-specific TKR instrumentation
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SAN DIEGO — The inherent advantages and disadvantages regarding the use of patient-specific instrumentation for total knee replacement make it a hot topic for debate, as evidenced by several presentations here.
The presentations were part of a symposium at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons. The symposium, which focused on debates regarding contemporary issues in total knee replacement, featured a number of surgeons well-versed in the field — including Adolph V. Lombardi, MD, and Thomas P. Vail, MD, who debated the use of patient-specific guides.
 Adolph V. Lombardi |
Patient-specific guides work
“I think the keys to durability are to restore the mechanical axis and balance the flexion/extension gap,” Lombardi said. “I think there are various ways we can restore the mechanical axis.”
Lombardi talked about cadaveric studies in which he has verified that current patient-specific alignment guides are a viable solution.
“We did nine bilaterals, and we showed, with [postoperative] CT scans, that we were better able to reconstruct the alignment using the custom guides than using our standard instruments,” he said.
To further support his stance, Lombardi added analysis of 91 custom-guided procedures and 91 conventional procedures — in which he found total error outliers of 1.5% with custom guides compared with 6% with conventional instrumentation.
Further analysis included two different centers and focused on results from two separate centers, looking at the intersection of the central-third, hip-knee angle, and individual component positioning. With patient-specific guides, 87% of patients fell within the central third vs. 77% with manual instruments — “a certain improvement,” Lombardi said.
“I think the question of mechanical axis restoration as a prerequisite for successful total knee has been in question, but my take-home message is ‘thou shalt not varus,’ and I have better been able to do that with patient-specific guides,” Lombardi concluded.
The economic paradigm
 Thomas P. Vail |
“If the message here is to take one of these simple guides, make a small incision, plug it in there and do a perfect total knee — that is great, sign me up,” Vail said. “But, I really think there is more to it.”
Vail noted that while there is some cadaver evidence for the support of patient-specific guides, the clinical evidence is lacking and, thus, the question remains as to whether the early results are generalizable.
Furthermore, he added, patient-specific guides do not solve the primary problems with knee replacement.
“The major problems in knee replacement now have to do with infection or aseptic loosening,” Vail said. “Will it solve these problems? Not sure.”
Vail also talked about the economical side of the issue, discussing quality cost and overall value in health care. He noted added costs of imaging, instrument fabrication and potential out-of-pocket costs when payers deny technology — all for an implant similar to what they would have received otherwise.
“Think about the economic paradigm,” Vail said. “The total economic package is not getting bigger, but potentially as surgeons our part is getting smaller because of this unreimbursed time to estimate size, have standard equipment available for back-up … plus the costs of imaging.”
“It may not look so good going forward,” he added.
References:
- Lombardi AV. Patient-specific instruments primary TKA: For. Part of symposium B, “Debates on contemporary issues in total knee replacement.” Presented at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons. Feb. 15-19, 2011. San Diego.
- Vail TP. Patient-specific instruments primary TKA: Against. Part of symposium B, “Debates on contemporary issues in total knee replacement.” Presented at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons. Feb. 15-19, 2011. San Diego.
Disclosures: Lombardi receives royalties from Biomet and Innomed. He also is on the speakers bureau for, is a paid consultant for, and receives research or institutional support from Biomet. Vail receives royalties from and is a paid consultant for DePuy. He also owns stock in Pivot Medical.
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