Better TKA outcomes recorded after tissue balancing

Study showed no difference in results when surgeons used balancers.

Soft tissue balancing remains paramount for good total knee arthroplasty results. A new study supports this practice and finds no significant differences between the extent of tissue release.

In a study of 407 patients, researchers found that knees that remained imbalanced postoperatively showed the least change in outcome scores, while those that became balanced after surgery showed the most improvement. “The key message to leave with you today is that balancing an imbalanced knee significantly improves knee outcome,” said Linda Unitt, MCSP, SRP, a physiotherapist with the Birmingham Heartlands & Solihull NHS Trust in Birmingham, England.

Unitt and her colleagues also found no major clinical or functional differences between knees that received minimal, large or extensive soft tissue releases. In addition, they didn't see any difference in outcomes between cases where surgeons used knee-balancing tools and those that did not.

Multicenter study

In a one-year follow-up of patients, researchers found 35 wound infections, Unitt said during her presentation at the 7th European Federation of National Associations of Orthopaedics and Traumatology Congress. Four hematomas required release. Two patients needed revisions (one for infection and one for pain due to implant loosening) and 29 required manipulation, but researchers reported no connection between the complications and release size, postoperative balance or balancer use, she said.

The findings are part of a larger, multicenter study consisting of 506 TKA patients. The research includes 230 men and 276 women with a primary diagnosis of osteoarthritis. Most patients showed preoperative varus deformities and had a mean age of 70 at the time of surgery, Unitt said.

Seven surgeons performed the operations. Five surgeons incorporated conventional, non-instrument balancing techniques, while two used a balancer. The surgeons who used a balancer recorded preoperative knee balance and examined balance after surgery with the knees in extension and at 90° of flexion, Unitt said.

Despite the use of a balancer, all surgeons used the same surgical technique and implanted patients with the Kinemax prosthesis (Stryker Corp.). To control for extraneous variables, patients followed the same postoperative routines.

An independent observer examined participants postoperatively at six and 12 weeks and 12 months. Assessments included Roentographic and Evaluation Scoring System measures, Oxford Knee scores and data from the American Knee Society Clinical Rating System, Unitt said. In addition, researchers performed analysis on the following four categories: knee balance, the extent of release, balancer use and range of motion.

Researchers defined balance as 3° on side-to-side 0, Unitt said. They also considered balance as the final calculation before tensioning, she said.

Researchers categorized knees in the four following groups: balanced knees that remained balanced postoperatively, knees that became unbalanced after surgery, unbalanced knees that remained unbalanced after operation, and unbalanced knees that became balanced postoperatively.

“For the two surgeons using the balancer technique, [we saw] a significant difference in the change in knee scores,” researchers wrote in their abstract. “The knees left imbalanced had substantially lower change scores and, interestingly, the imbalanced-to-balanced group showed the most change,” Unitt said.

In a comparison of minimal, larger and extensive tissue releases, investigators saw no significant differences in functional and Knee Society score changes among cohorts, she said. However, Unitt said that researchers noted “a trend of failure” in the extensive release group.

Balancer use

Investigators also evaluated differences between surgeries performed with balancers and those without balancing instruments.

“Again, there is no difference in the changes in Oxford Knee Score or in the functional knee scores using the clinical rating system,” Unitt said. Similarly, a comparison regarding the range of motion showed no significant differences when researchers assessed the extent of release, balancer use or final balance.

She said the research disproves theories that larger releases lead to worse results. “So, in conclusion, in [the] short term, extensive soft tissue releases do not lead to poorer outcomes or increase complication rates,” Unitt said. “When compared to traditional and balanced guide techniques, there is no significant differences in outcomes.”

For more information:
Unitt L, Sambatakakis A, Briggs DJ, et al. Measured soft tissue balancing in total knee arthroplasty: Early results of a multi-center study. #F75. Presented at the 7th European Federation of National Associations of Orthopaedics and Traumatology. June 4-7, 2005. Lisbon, Portugal.