Gap balancing versus measured resection in TKA—Evidence for/against gap balancing

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When it comes achieving correct femoral component positioning during TKA, one commonly used technique is gap balancing. This method is successfully employed by many surgeons and involves balancing tension and flexion gaps before femoral bone cuts are made. Here, in part 2 of our article series, we explore gap balancing and some of the positive and negative commentary surrounding this technique.

 

 

Some schools of thought maintain that the success of total knee arthroplasty (TKA) relies - among other things - on achieving symmetric, balanced flexion and extension gaps [1]. Indeed, soft tissue management has been identified by some as more important to outcomes than bone management [2].

If femoral component malrotation is present, it can result in decreased patient satisfaction (pain) and implant disfunction [3] via altered tibiofemoral kinematics [4, 5]. Malrotation can also cause patellofemoral complications and instability. This was directly correlated to the combined (femoral and tibial) internal component rotation by Berger et al. [6] It has also been suggested that if relative rotational mismatch is kept within ±5° (surgical norms), then knee axial rotation during flexion is more controlled and more likely to deliver a better outcome [5].

Gap balancing has been shown to produce desirable outcomes, particularly because balancing is done independent of bony anatomy, eliminating confusion around intraoperative landmarking that could be compromised by bone deformities and individual anatomical variation [7, 8].

Matthew Abdel, orthopedic surgeon at the Mayo Clinic in Rochester, US, finds the technique, “particularly useful for patients with distal femoral fractures where anatomic landmarks are displaced and may make a measured resection technique difficult.” Philipp von Roth, orthopedic surgeon at the Charité-University Hospital in Berlin, Germany, feels that the “gap balancing technique is optimal for redressable varus- or valgus deformities and in case of difficulties identifying the anatomical landmarks with intact ligaments.”

 

Two gap balancing techniques

While measured resection is a technique used to determine femoral component rotation, this article will examine gap balancing and its two recognized sequences, looking at the pros and cons. See our interview on why surgeons use one or the other technique.

In gap balancing, ligaments are released before femoral bone cuts are made [7]. One technique we will discuss involves balancing the flexion gap first; the other technique first balances the joint in extension, then returns to address the flexion gap in relation to the previously balanced extension gap [7]. Both require sequential soft tissue balancing [9].

Remove all osteophytes

Both techniques demand the removal of all osteophytes (including posterior femoral and tibial) before soft tissue releases. Ramappa et al. reminds surgeons about “the importance of meticulous osteophyte excision” [10]. These bony projections tension adjacent ligaments, which may produce flexion gap asymmetry and femoral component malrotation [7], and increase the likelihood of interaction between implant components and surrounding tissue, to the detriment of the patient [10].

Success tied to accurate tibial cuts

The success of gap balancing, for both sequences, hinges on a precise proximal tibial cut; correct depth and alignment on the coronal and sagittal planes is critical to avoid femoral component malrotation [8]. If the resection is varus or valgus then either internal or external rotation, respectively, of the femoral component will occur [7, 8]. This can result in “a mismatch of flexion and extension gap dimensions” [7]. The tibial cut is used as a reference point for femoral resections, further reaffirming the importance of accuracy in the tibial resection.

 

If you start with the flexion gap

If a surgeon chooses to balance the extension gap first they are looking for parallel alignment of the tibial cut with the transepicondylar axis, which will be perpendicular to the anteroposterior axis. Required soft tissue releases are performed after the joint is correctly tensioned in flexion, using the above alignments to guide releases (Fig. 1). After this, the extension gap addressed [7].

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Access full article here
  • If you start with the flexion gap
  • If you start with extension balancing
  • Symmetric gaps
  • The case for gap balancing
  • The case against gap balancing
  • When not to use gap balancing
  • Conclusion
  • References

Part 1 | Brief comparison of the techniques

Read here

Part 3 | Evidence for/against measured resection

Read here

Additional AO resources

Access videos, tools, and other assets to learn more about this topic.

Contributing experts

This series of articles was created with the support of the following specialists (in alphabetical order):

Matthew P Abdel MD

Mayo Clinic
Rochester, United States

Philipp von Roth MD

Charité—University Medicine Berlin
Berlin, Germany

This issue was created by Word+Vision Media Productions, Switzerland

 

References

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  2. Peters CL. Soft-tissue balancing in primary total knee arthroplasty. Instr Course Lect. 2006 55:413–417.
  3. Poilvache PL, Insall JN, Scuderi GR, et al. Rotational landmarks and sizing of the distal femur in total knee arthroplasty. Clin Orthop Relat Res. 1996 Oct; (331):35–46.
  4. Heyse TJ, El-Zayat BF, De Corte R, et al. Internal femoral component malrotation in TKA significantly alters tibiofemoral kinematics. Knee Surg Sports Traumatol Arthrosc. 2017 Nov 11. doi: 10.1007/s00167-017-4778-1. [Epub ahead of print]
  5. Harman MK, Banks SA, Kirschner S, et al. Prosthesis alignment affects axial rotation motion after total knee replacement: a prospective in vivo study combining computed tomography and fluoroscopic evaluations. BMC Musculoskelet Disord. 2012 Oct 13:206. doi: 10.1186/1471-2474-13-206.
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