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Postoperative changes in CPAK-classification do not significantly influence patient-reported outcome measures following conventional or robotic-assisted total knee arthroplasty: A randomised controlled trial

  • 0Sint-Trudo Hospital, Sint Truiden, Belgium.
Knee Surgery, Sports Traumatology, Arthroscopy : Official Journal of the Esska +

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July 13, 2025

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July 13, 2025

View abstract on PubMed

Summary

This summary is machine-generated.

Total knee arthroplasty outcomes were not affected by changes in Coronal Plane Alignment of the Knee (CPAK) classification. Both conventional and robotic-assisted techniques showed similar improvements in patient-reported outcomes, regardless of CPAK alignment.

Area Of Science

  • Orthopedic Surgery
  • Biomechanical Engineering
  • Clinical Outcomes Research

Background

  • Coronal Plane Alignment of the Knee (CPAK) classification is a system used to categorize knee alignment.
  • Understanding how CPAK classification changes affect patient outcomes after total knee arthroplasty (TKA) is crucial for surgical technique.
  • Both conventionally aligned TKA (CTKA) and imageless robotic-assisted TKA (RATKA) are employed, with varying impacts on alignment preservation.

Purpose Of The Study

  • To investigate the impact of pre- and postoperative CPAK classification changes on patient-reported outcome measures (PROMs).
  • To determine the rate of CPAK classification change in CTKA versus RATKA.
  • To test the hypothesis that PROM improvements are comparable whether CPAK classification is preserved or altered postoperatively.

Main Methods

  • A prospective randomized controlled trial involving 180 patients undergoing either CTKA or RATKA.
  • Pre- and postoperative CPAK classification assessment.
  • Collection of PROMs (Knee Society Score, Oxford Knee Score, VAS, EuroQol-5D, patient satisfaction) at baseline, 3, and 12 months.

Main Results

  • Native CPAK classification was preserved in 31% of CTKA and 41% of RATKA patients.
  • Postoperatively, CPAK II was most common (40% CTKA, 49% RATKA), followed by CPAK V.
  • Both surgical techniques demonstrated significant PROM improvements at 3 and 12 months, irrespective of CPAK classification changes.

Conclusions

  • Short-term functional outcomes after TKA are not significantly influenced by maintaining or altering CPAK classification ('In-the-box' vs. 'Out-of-the-box').
  • CTKA and RATKA provided comparable improvements in PROMs.
  • Alignment strategy should prioritize individual anatomy and soft-tissue balance over strict CPAK matching, even if it requires greater soft-tissue release.

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