Total knee arthroplasty in patients with degenerative spine disease: does spinal fusion affect outcomes? A matched comparative analysis using a national database.

Background: The need for total knee arthroplasty (TKA) and spinal fusion (SF) for degenerative spine disease (DSD) is increasing. However, it is still unknown if prior SF for DSD impacts outcomes following TKA. This study aims to fill this gap by comparing the risk of complications and revisions in patients undergoing TKA with DSD between patients with and without SF.

Methods: This study is a retrospective review of the PearlDiver Mariner Database between 2010 and 2020. On the basis of whether or not patients had had prior SF, the patients undergoing TKA were divided into two groups: patients with DSD and SF and patients with DSD and without SF. The two groups were matched on the basis of age, gender, the Charlson Comorbidity Index (CCI), and obesity. Surgical complications (mechanical loosening, prosthetic dislocation, periprosthetic fractures, and stiffness) and revisions at 1, 2, and 3 years were compared between the groups.

Results: The patients in the TKA with DSD and no SF cohort were older (64.9 ± 8.4 versus 63.3 ± 8.1 years, p < .001), had higher CCI (2.0 ± 2.2 versus 1.6 ± 2.0, p < .001), and had a lower rate of obesity (58.7% versus 61.7%, p < .001). After being matched, 8887 patients remained in each group. There was a higher rate of stiffness and manipulation under anesthesia (MUA) in the no-fusion cohort at 1 year (0.7% versus 0.1%, p < .001; and 0.5% versus 0.2%, p < .001, respectively), 2 years (1.2% versus 0.5%, p < .001; and 1.1% versus 0.6%, p < .001, respectively), and 3 years (1.7% versus 0.7%, p < .001; and 1.6% versus 0.9%, p < .001, respectively).

Conclusions: This study shows no increase in risk of surgical complications and revisions after TKA in patients with DSD and SF compared with patients without SF. Notably, SF was shown to be protective of stiffness and MUA after TKA in patients with DSD.