'Extended' restricted kinematic alignment results in decreased residual medial gap tightness among osteoarthritic varus knees during robotic-assisted total knee arthroplasty

Krishna K Eachempati; Apurve Parameswaran; Vinay K Ponnala; Apsingi Sunil; Neil P Sheth

doi:10.1302/2633-1462.58.BJO-2024-0054.R1

'Extended' restricted kinematic alignment results in decreased residual medial gap tightness among osteoarthritic varus knees during robotic-assisted total knee arthroplasty

Bone Jt Open. 2024 Aug 2;5(8):628-636. doi: 10.1302/2633-1462.58.BJO-2024-0054.R1.

Authors

Krishna K Eachempati¹, Apurve Parameswaran¹, Vinay K Ponnala¹, Apsingi Sunil¹, Neil P Sheth²

Affiliations

¹ Department of Orthopaedics, Medicover Hospitals, Hyderabad, India.
² Penn Orthopaedics at Pennsylvania Hospital, University of Pennsylvania, Philadelphia, Pennsylvania, USA.

PMID: 39089685
PMCID: PMC11299516
DOI: 10.1302/2633-1462.58.BJO-2024-0054.R1

Abstract

Aims: The aims of this study were: 1) to describe extended restricted kinematic alignment (E-rKA), a novel alignment strategy during robotic-assisted total knee arthroplasty (RA-TKA); 2) to compare residual medial compartment tightness following virtual surgical planning during RA-TKA using mechanical alignment (MA) and E-rKA, in the same set of osteoarthritic varus knees; 3) to assess the requirement of soft-tissue releases during RA-TKA using E-rKA; and 4) to compare the accuracy of surgical plan execution between knees managed with adjustments in component positioning alone, and those which require additional soft-tissue releases.

Methods: Patients who underwent RA-TKA between January and December 2022 for primary varus osteoarthritis were included. Safe boundaries for E-rKA were defined. Residual medial compartment tightness was compared following virtual surgical planning using E-rKA and MA, in the same set of knees. Soft-tissue releases were documented. Errors in postoperative alignment in relation to planned alignment were compared between patients who did (group A) and did not (group B) require soft-tissue releases.

Results: The use of E-rKA helped restore all knees within the predefined boundaries, with appropriate soft-tissue balancing. E-rKA compared with MA resulted in reduced residual medial tightness following surgical planning, in full extension (2.71 mm (SD 1.66) vs 5.16 mm (SD 3.10), respectively; p < 0.001), and 90° of flexion (2.52 mm (SD 1.63) vs 6.27 mm (SD 3.11), respectively; p < 0.001). Among the study population, 156 patients (78%) were managed with minor adjustments in component positioning alone, while 44 (22%) required additional soft-tissue releases. The mean errors in postoperative alignment were 0.53 mm and 0.26 mm among patients in group A and group B, respectively (p = 0.328).

Conclusion: E-rKA is an effective and reproducible alignment strategy during RA-TKA, permitting a large proportion of patients to be managed without soft-tissue releases. The execution of minor alterations in component positioning within predefined multiplanar boundaries is a better starting point for gap management than soft-tissue releases.