Similar pain requirements between bilateral, unilateral TKR patients

Bilateral patients may require up to 1 day of additional hospitalization compared to unilateral TKR patients.

Bilateral total knee replacement patients experience similar pain levels to unilateral patients during hospitalization, a new study shows. However, bilateral patients may initially require slightly more pain medication and may need additional time to regain ambulation, the authors note.

Robert S. Powell, MD, and colleagues at the Scripps Clinic in La Jolla, Calif., conducted a retrospective study comparing narcotic use, perceived pain and postop ambulatory ability between bilateral and unilateral total knee replacement (TKR) patients. They published their results in the Journal of Arthroplasty.

The study included 59 bilateral TKR patients with a mean age of 67.83 years. These patients were matched to a group of 59 unilateral TKR patients with a mean age of 67.71 years. Both groups contained 29 women and 39 men. Four surgeons performed all procedures using identical intraoperative protocols and implanted a posterior cruciate-retaining prosthesis, according to the study.

To compare pain medication use, the researchers converted narcotic requirements to dose equivalents (DE), with 1 DE equal to 10 mg of intramuscular morphine. They found that both groups had similar intraoperative narcotic requirement, averaging 2.01 ± 1.67 DE for unilateral patients and 2.06 ± 1.47 DE for bilateral patients.

Bilateral patients needed more pain medication during the first 48 hours postop, but both groups used similar amounts by 48 to 72 hours follow-up, according to the study.

“Combining the narcotic use for the first 72 hours after surgery, no statistically significant difference was noted ...,” the study authors said.

The researchers noted that bilateral patients had significantly higher analog scale-measured pain during the early postoperative period. But, again, no significant difference was noted between groups after the first day postop, according to the study.

The researchers did find a significant difference in walking ability, with bilateral patients lagging behind unilateral patients by about 1.5 days (P<.05). By day 3, bilateral patients could walk an average of 78.3 feet, while unilateral patients could walk an average of 169.1 feet.

Bilateral patients required significantly longer hospitalization, although it differed by less than one day (mean 3.15 days for unilateral patients vs. 4 days for bilateral patients; P<.001). Significantly more unilateral patients were also discharged home as opposed to a skilled nursing facility — 63% compared with 37% of the bilateral patients, according to the study.

“The authors are of the opinion that a patients needs to walk at least 50 feet to be safely discharged home. Using these criteria, unilateral patients, on average, reach this milestone between postoperative day 1 and postoperative day 2. Bilateral patients, on average, did not reach this milestone until postoperative day 3,” the authors said.

Both groups experienced similar rates of complications.

For more information:
Powell RS, Pulido P, Tuason MS, et al. Bilateral vs. unilateral total knee arthroplasty: A patient-based comparison of pain levels and recovery of ambulatory skills. J Arthroplasty. 2006;21:642-649.