Use of patient-matched cutting blocks provided increased fit accuracy in TKA
Click Here to Manage Email Alerts
BIRMINGHAM, England — Technology that researchers in the United Kingdom used to create patient-matched cutting blocks for total knee arthroplasty resulted in blocks that were precisely matched to the intraoperative femoral and tibial surfaces, according to data presented at the British Orthopaedic Association Congress, here.
Andrew J. Porteous, MBChB, FRCS(Ed), MSc(Orthopaedic Engineering), FRCS(Tr&Ortho), of the department of trauma and orthopaedics at Southmead Hospital in Bristol, U.K., and colleagues created patient-matched cutting blocks that fit the ends of the femur and the tibia using a 3-D model of the surface of the knee based on a MRI scan. The 3-D model was then considered, with surgeon preferences, to create a preoperative plan to determine which components to use in the operating room and where to position the cutting slots in the custom cutting blocks.
Porteous presented data at the British Orthopaedic Association Congress on the first 105 total knee arthroplasty (TKA) cases in which this technology was used. He told Orthopaedics Today Europe that the take-home message of his presentation was, “The technology allows the manufacture of blocks that provide a good or excellent fit in 99.5% of cases. Match of the planned size to actual size used improved if surgeons took the time to check plans preoperative (95% up to 100% on the femoral side and 89% up to 98% on the tibial side).”
Operative notes
In addition to MRIs, all patients had long leg radiographs. Eight patients required additional imaging, yielding a 7% unexpected re-imaging rate, Porteous said.
Porteous said the blocks take about 6 weeks to make.
“There were 14 cases on top of the 105 within that period that we couldn’t proceed to do the cases with — three for metallic artifacts on MRI and six with expedited surgery dates so the blocks were not ready, and perhaps not unexpected in this age group, there were five that were medically deferred or terminated,” he said at the meeting.
Researchers obtained operative notes that clearly discussed TKA component fit in 93 cases.
“The femoral block was always reported to have excellent fit,” Porteous said.
In 91 cases with detailed operative notes and the preoperative plan available for comparison, researchers found the femur was never upsized, but it was downsized from the plan in five cases. “If the surgeon spent the time to go and check the plan, this increased accuracy from 95% to 100% in the femur,” Porteous said in his presentation. “So those [five cases] could have been predicted from checking the plan.”
Avoid overhang
In the tibial component, surgeons needed to downsize twice due to excessive osteophytes that had been removed, and they upsized eight times.
“The surgeons had also set their preference on the tibia for downsizing so as not to overhang, so some of that includes cases between size, but again, all of those could have been predicted by the plan,” Porteous said.
In the tibial component, accuracy was 89% based on results of the study and the accuracy increased to 98% when the surgeon approved the plan and modified it before surgery.
Overall, the researchers reported that of the 7.5% of cases of “size variation from plan,” 5.5% could have been avoided by closer inspection of the preoperative plans.
“Within a state health service, organizing and managing the process does require a dedicated team and some effort,” Porteous told Orthopaedics Today Europe. – by Tina DiMarcantonio
- Reference:
- Porteous A. Paper #982. Presented at: British Orthopaedic Association Congress; Oct.1-4, 2013; Birmingham, England.
- For more information:
- Andrew J. Porteous, MBChB, FRCS(Ed), MSc(Orthopaedic Engineering), FRCS(TR&Ortho), can be reached at Southmead Way, Bristol, Avon BS10 5NB, United Kingdom; email: andrew.porteous@nbt.nhs.uk.
Disclosure: Porteous’ department receives research funding from Stryker, Corin and Smith & Nephew.