Lumbar spine problems linked to lower knee function scores before and after TKA
Although total knee arthroplasty (TKA) generally results in excellent pain relief, approximately 20 percent of patients have persistent functional deficits that affect their quality of life, noted William C. Schroer, MD, during the 2015 annual meeting of the American Association of Hip and Knee Surgeons.

Dr. Schroer reported that lumbar spine problems are a common cause of functional disability in TKA patients. In the study he and his colleagues conducted, patients with a history of lumbar spine problems had significantly worse knee function scores.

The results of this study also confirm multiple previous studies that have found that poor preoperative knee function is linked to poor TKA function.

"The findings of this study suggest that poor preoperative function—which has been consistently associated with poor postoperative function—is frequently due to unrelated spine disability," asserted Dr. Schroer.

Conducting the study
The investigators used a primary TKA database that prospectively collects patient demographics, surgical and knee-specific data, Oxford Knee Scores (OKS), and Knee Society (KS) pain and function scores, both prior to surgery and during postoperative follow-up. In total, they collected data on 1,156 consecutive primary TKAs performed by the principal investigator between July 2010 and July 2012. Patients were invited to complete a questionnaire by mail that posed subjective questions about a general history of back problems as well as specific, objective questions used to calculate the Oswestry Disability Index (ODI), which Dr. Schroer noted is currently the most commonly employed outcome measure for lumbar-specific spinal disability.

Of the 1,156 consecutive primary TKA patients, 691 patients (237 males and 454 females; average age, 69 years [range, 49 years to 89 years]) completed the spine questionnaire. The investigators compared the demographic and knee-specific data of the responders to non-responders in an effort to minimize bias resulting from the voluntary nature of the response sample.

The same surgical technique and perioperative protocol was used for all TKA patients. In addition, the perioperative management program included preoperative education, and management and prevention of perioperative pain and nausea, using a multimodal protocol. Postoperative therapy focused on restoring knee range of motion and returning patients to activities. Follow-up occurred at 3, 6, and 12 weeks following surgery, with extended office follow-up visits at 1 and 3 years.

Assessing results
In patients who completed questionnaires, knee pain and function scores at most recent follow-up improved significantly from preoperative scores (P<0.0001). however, improvement in ks function scores was significantly less than that in ks pain scores (29.0 versus 45.4,>P<0.0001). consistent with previous studies of large tka cohorts, ks function scores "improved less consistently with wider variability in improvement" than ks pain scores, according to dr. schroer. >

More than half (371 patients; 54 percent) of those who completed questionnaires reported a history of back problems, including daily low back pain, pain that limited activities, and back surgery. OKS scores were significantly lower in patients who reported a history of back problems than in patients without back problems, both prior to TKA (36.9 versus 34.8, P = 0.0006) and after TKA (20.2 versus 17.0, P < 0.0001). However, both groups noted similar levels of improvement (16.7 versus 17.8). Patients with back problems had significantly worse KS function scores than those without back problems, both preoperatively and postoperatively. KS pain scores, however, were similar before and after TKA, regardless of patients' self-reported spine history. In addition, a patient's degree of spine disability, as determined by the ODI, correlated directly with worse OKS and KS function scores.

Although OKS, KS pain, and KS function scores significantly improved after TKA, Dr. Schroer noted that, "in this review of fully recovered primary TKA patients, the majority had spine problems.

"The results of this study suggest that spine pathology is a significant cause of functional limitation," he added. These findings support the important role back pain plays in relation to poor function and poor satisfaction reported in TKA patients in large registry databases. To accurately interpret knee function outcomes in these databases, noted Dr. Schroer, a spine disability variable should be part of the analysis.

Dr. Schroer's coauthors for "Total Knee Outcomes Correlate Strongly with Spine Disability" included Paul G. Diesfeld, PA-C, Angela R. LeMarr, RN, Diane J. Morton, MS, and Mary E. Reedy, RN. The authors' disclosure information can be accessed at www.aaos.org/disclosure

Jennie McKee is a senior science writer for AAOS Now. She can be reached at mckee@aaos.org

Bottom Line

• Investigators obtained prospective data on 1,156 consecutive primary TKAs performed over a 2-year period. Of these patients, 691 voluntarily completed a spine questionnaire, enabling researchers to calculate ODI scores.
• OKS scores were significantly worse in patients who reported a history of back problems in comparison to patients without back problems, both before and after undergoing TKA.
• Patients with back problems had significantly worse KS function scores, both before and after surgery, compared to those without back problems. KS pain scores, however, were similar before and after TKA, regardless of patients' self-reported spine history.