Knee stiffness following total knee arthroplasty: comparison of computer assisted surgery and conventional technique

David Russell, Chris Ugbolue, Julie Smith, Mark Blyth, Philip Rowe

Research output: Contribution to conferencePaper


Computer assisted surgery techniques have yet to demonstrate any significant functional benefit over conventional methods in total knee arthroplasty. Outcome measures studied to-date are often subjective relying on patient interpretation and scoring, especially of the term
‘stiffness’. However, this can be measured objectively as Nm/degree of joint rotation.

We used a novel purpose-built knee dynamometer (PBKD) to
measure absolute end of range stiffness in a randomly selected sample of patients from a prospective, randomised trial of computer assisted (n=24) versus conventional (n=22) total knee arthroplasty. Implant position from postoperative computed-tomography scanning along with maximum
moment of the quadriceps and hamstrings at 90˚ were analysed to detect any correlation with absolute knee stiffness.

Mean stiffness while extending from100˚-90˚ was
0.51±0.28Nm/deg for computer assisted and 0.52±0.2Nm/deg for conventional arthroplasty. Flexing from 90˚-100˚, mean stiffness was 0.64±0.25Nm/deg and 0.68±0.17Nm/deg respectively. Across the entire cohort of patients, correlation coefficient was calculated to quantify
relationship between stiffness (extending and flexing) and implant position: tibial sagittal alignment (extending -0.43, flexing 0.48, see figure), tibia coronal alignment (0.34, 0.38), femorotibial component alignment match (0.34, 0.32), mechanical femorotibial alignment (0.34, 0.32), maximum quadriceps moment at 90˚ knee flexion (0.2, 0.41), and
maximum hamstring moment at 90˚ knee flexion (0.16, 0.33).

No significant difference in postoperative knee stiffness following computer assisted and conventional arthroplasty carried out by a surgeon specializing in knee reconstruction can be detected using this methodology. Implant position may be a causal factor in knee stiffness following arthroplasty, which may limit rehabilitation and functional
Original languageEnglish
Publication statusPublished - 4 Aug 2013
Externally publishedYes
EventXXIV Congress of the International Society of Biomechanics: XV Brazilian Congress of Biomechanics - Natal, Brazil
Duration: 4 Aug 20139 Aug 2013 (Conference details)


ConferenceXXIV Congress of the International Society of Biomechanics
Abbreviated titleISB 2013 Brazil
Internet address


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