TKA and HTO navigation protocols yield different limb alignment outcomes

Issue: April 2013

In a presentation scheduled to be held during the upcoming EFORT Congress, Seung-Suk Seo, MD, plans to discuss a study he and his colleagues at Bumin Hospital, in Busan, Korea, conducted into total knee arthroplasty surgery performed with computer assistance.

Perspective from Justin P. Cobb, MD

“It is a hot issue in the knee arthroplasty societies. In my experience, alignment of the lower limb is important for implant longevity. There must be an acceptable range of lower limb alignment. Traditionally, within 3° varus/valgus in mechanical axis (MAX) has been recommended,” Seo told Orthopaedics Today Europe in an interview prior to the meeting.

In their investigation, Seo and colleagues found differences between the preoperative and postoperative lower limb MAX that they measured in the same knee of 71 patients undergoing total knee arthroplasty (TKA) surgery. These differences were significant at three levels, based on the measurements the team made with radiographs and during computer-assisted TKA surgery, according to the abstract.

Seo and colleagues used the TKA and high tibial osteotomy (HTO) protocols offered with the OrthoPilot computer-aided surgery system (B. Braun Aesculap; Tuttlingen, Germany). These two protocols use either bony or soft tissue anatomical landmarks around the knee, respectively, for registration.

The surgeon performs high tibial osteotomy (HTO) registration (top) preoperatively at the knee joint center. The resultant registration area (bottom) is shown according to the HTO protocol.

The lower limb alignment findings from the investigation were unaffected by the weight, height, range of motion and age of the patients, according to the results.

“Our data showed the preoperative difference between radiography and HTO [protocol] and [between radiography and] TKA protocol was 3.5° and 4.5°, respectively, and that the postoperative difference between radiograph and TKA was 2.2°,” Seo said. “We suspect preoperative deformity makes the difference larger.”

However, he noted, it is difficult say what amount of MAX is in the safe range for patients.

All the TKA procedures in the study were performed for primary osteoarthritis. – by Susan M. Rapp

Reference:
Seo S-S. Paper #13-2053. Scheduled to be presented June 7 at the EFORT Congress; June 5-8, 2013; Istanbul.
For more information:
Seung-Suk Seo, MD, can be reached at Department of Orthopedic Surgery, Bumin Hospital, 380-4, Dwokcheon-Dong, Buk-Gu, Buson, Korea 616-819; email: wellknee@gmail.com.

Disclosure: Seo has no relevant financial disclosures.

Perspective

Justin P. Cobb, MD

This Korean study done with the OrthoPilot navigation system (B. Braun Aesculap, Tuttlingen, Germany) highlights the difficulty of imaging and navigation in knee arthroplasty. The navigating surgeon delivers precise surgery, but the results are not confirmed on postoperative standing 2-D radiographs. The confirmed conventional surgeon will gain comfort from this study using image-free technology.

Increasingly surgeons are using patient-matched instruments based upon supine axial imaging without any kinematic input. Like the navigators, this group can tell us that they achieve their intraoperative goals, but long leg standing films may not reflect their results either. Is it time for a new gold standard beyond long leg films?

Justin P. Cobb, MD

Chair, Section of Orthopaedics MSk Lab

Imperial College London

London

Disclosures: Cobb is a shareholder in and receives royalty payments from Stanmore Implants. He is a paid consultant to MatOrtho, and received grant support from CeramTec, DePuy and Biomet.

TKA and HTO navigation protocols yield different limb alignment outcomes

For more information:

Perspective