Is acquired idiopathic stiffness after primary total knee arthroplasty a thing? And, if so, what are the potential risk factors for its development? A Rochester, Minnesota based team from the Mayo Clinic mined several databases between 2002 and 2017 to answer those two questions. Their resulting paper, “Acquired Idiopathic Stiffness After Total Knee Arthroplasty,” was published in the July 17, 2019 edition of The Journal of Bone and Joint Surgery.
Idiopathic Stiffness After TKA: Is This a Thing?
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Matthew P. Abdel, M.D., professor of Orthopedic Surgery at the Mayo Clinic College of Medicine in Minnesota, outlined the issue to OTW: “Most people understand that stiffness is a common reason for suboptimal clinical outcomes after primary total knee arthroplasty. However, there is a lack of consensus on its definition. More importantly, people confuse it with a specific histopathologic subcategory of arthrofibrosis.”
“As such, we refined the definition of ‘acquired idiopathic stiffness’ and selected for patients who truly had arthrofibrosis in our investigation. Thereafter, we completed a systematic review and meta-analysis of the literature.”
According to the authors, “Studies that included patients with stiffness after primary total knee arthroplasty were screened with strict inclusion and exclusion criteria to isolate the subset of patients with acquired idiopathic stiffness unrelated to known extrinsic or surgical causes. Three authors independently assessed study eligibility and risk of bias and collected data.”
Abdel and his team included 35 studies in their review. In 63% of the studies, the authors defined “stiffness” as a range of motion of <90° or a flexion contracture of >5° at 6 to 12 weeks postoperatively. In reviewing the data, the researchers found that the prevalence of acquired idiopathic stiffness after primary total knee arthroplasty was 4%—this did not differ according to age. The team also found that acquired idiopathic stiffness was significantly lower in males than females as well as in patients with a body mass index of <30 kg/m2 versus those with a BMI of ≥30 kg/m2.
Dr. Abdel summarized his team’s findings to OTW, “We came to a consensus that contemporary literature supported the following definition of acquired idiopathic stiffness: a range of motion of less than 90 degrees persisting for greater 12 weeks in patients without complicating factors. Moreover, we found the prevalence to be 4% after primary total knee arthroplasty, with females and obese patient being at increased risk.”
Dr. Abdel notes that he is a paid consultant for Stryker.
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This is a fascinating development. In my practice we've seen similar outcomes with the revised protocol. The key differentiator seems to be patient selection criteria. Has anyone else noticed the correlation with BMI thresholds?
Great point. I'd push back slightly on the conclusion, the sample size in the cited study is too small to draw population-level inferences. That said, the directional signal is compelling and worth a larger RCT.
We implemented a similar approach last year. Early results are promising but we're still gathering 12-month follow-up data. Happy to share our protocol if anyone is interested.
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