Citation: Elmallah R, Mistry J, Cherian J, Chughati M, Bhave A, Roche M, Mont M. Can we really “feel” a balanced total knee arthroplasty. J Arthroplasty 31 (2016). S102-S105.
Approximately 20% of patients report dissatisfaction after undergoing total knee arthroplasty (TKA).1 Patients may experience complications with knee stiffness, pain and/or instability, which may result from soft tissue imbalance.2,3 Determining whether a knee is “balanced” is based on the surgeon’s subjective judgment, operative experience and skill.
The introduction of newer technologies has allowed for objective measurements of soft tissue balancing throughout knee range of motion. A wireless, intraoperative sensor tibial insert has been designed to measure intercompartmental loads of the knee to provide quantitative feedback of the medial and lateral compartments during TKA trialing.4 When using the device, the surgeon will perform the TKA in the typical manner and insert the sensor into the knee only after they believe it is balanced to guide additional balancing, cuts, and releases. Past research has demonstrated that adequate soft tissue balancing contributed to improved TKA outcomes.4,5
This study compared the use of sensor technology to the 30-year surgeon experience regarding
(1) compartment loads,
(2) soft tissue releases and
(3) component orientations.
Twenty-two patients undergoing TKAs were evaluated prospectively in a pilot series and divided into two cohorts: sensor-guided balancing (n = 10), or manual gap balancing (n = 12). Both groups were asked to use the sensor tibial insert trial to evaluate congruity and contact loads before applying cement to the final implant. In the manual gaping cohort, the surgeon was blinded and unaware of the values to eliminate bias from surgery performance. In the sensor cohort, the surgeon was unblinded and placed the sensor into the knee after they believed it was balanced; then used the data to guide further soft-tissue balancing and component position. Load measurements were taken at 10°, 45° and 90° (Figure 1).
Figure 1: Blinded vs Unblinded
The sensor cohort had lower medial and lateral compartment loading, lower mean differences in intercompartment loading, and performed more soft tissue releases compared to the manual gap cohort. The additional 10 releases were performed as a result of sensor evaluation, which would not have been done otherwise during manual-gap balancing. Manual balancing relies on the surgeon’s subjective assessments and may result in uneven loads, which may be associated with poor patient outcomes. The results from this study show sensor-balanced TKAs provide objective feedback to perform more soft tissue releases that may potentially improve knee balancing and component position.
So now that we know from this work, as well as others1,4,5, that the sensor can help us obtain more balanced knees, we need to know whether these “balanced” knees by sensor-aided technology perform better. It would appear that this is self- evident, but we still need proof that more precisely done knees function more optimally clinically. An ongoing prospective randomized controlled trial presently being performed may help answer these questions.
Dr. Michael Mont is a paid consultant to OrthoSensor, Inc.
1. Gustke KA, Golladay GJ, Roche MW, et al. Increased satisfaction after total knee replacement using sensor-guided technology. Bone Joint J 2014;96-B(10):1333.
2. Sharkey PF, Hozack WJ, Rothman RH, et al. Insall Award paper. Why are total knee arthroplasties failing today? Clin Orthop Relat Res 2002;(404):7.
3. Wylde V, Hewlett S, Learmonth ID, et al. Persistent pain after joint replacement: prevalence, sensory qualities, and postoperative determinants. Pain 2011;152(3):566.
4. Gustke KA, Golladay GJ, Roche MW, et al. A new method for defining balance: promising short-term clinical outcomes of sensor-guided TKA. J Arthroplasty 2014;29(5):955.
5. Gustke KA, Golladay GJ, Roche MW, et al. Primary TKA patients with quantifiably balanced soft tissue achieve significant clinical gains sooner than unbalanced patients. Adv Orthopedics 2014;628695:2014.