No Correlation Between Serum Markers and Early Functional Outcome After Contemporary THA

Serum markers of inflammation and muscle damage have shown clinical utility in some areas of medicine, but their value in determining the invasiveness or in predicting the early functional outcomes after total hip arthroplasty (THA) has not been demonstrated. (1) Do serum markers of inflammation/muscle damage predict pain or early functional outcomes after contemporary THA performed through a direct anterior or miniposterior approach? (2) Do early functional outcomes as measured by in-hospital outcomes and clinical milestones differ between a contemporary direct anterior and miniposterior approach for THA? Between August 31, 2013, and September 1, 2014, all patients presenting as candidates for THA at our institution who had not already had preoperative blood draws (161) were recruited for this study. Forty-two patients failed these exclusion criteria, eight patients declined enrollment, and 11 were consented but did not complete the required preoperative blood tests. Recruitment stopped when 50 patients had been enrolled in both the direct anterior group and the miniposterior group (2n = 100) based on a priori power analysis. One high-volume surgeon performed all of the direct anterior approaches and three high-volume surgeons performed the miniposterior approaches. Groups did not differ with the numbers available in mean age (63 years; SD 10; range, 35-86 years), sex (52% female), or mean body mass index (mean 31 kg/m(2); SD 7 kg/m(2); range, 20-73 kg/m(2)). Serum markers measured including hemoglobin, hematocrit, myoglobin, creatine kinase (CK), C-reactive protein, interleukin-6, and tumor necrosis factor-alpha were collected at the preoperative clinic visit and on postoperative days 1 and 2 and compared with operative details, in-hospital complications, therapy progress, pain scores, and functional results from a milestone diary. Functional results evaluated included time to discontinue all narcotics and gait aids, independence with activities of daily living, return to driving a motor vehicle, and return to work. Serum markers after contemporary THA were not correlated with early functional outcomes either in-hospital or postdischarge. Specifically, no serum marker was predictive of the time to discontinue gait aids or narcotics, return to driving, climb stairs, or independence in activities of daily living (all p > 0.08). The patients receiving the direct anterior approach did have lesser elevations of CK levels than the patients undergoing the miniposterior approach (436 +/- 312 [direct anterior {DA}] versus 1071 +/- 459 [miniposterior {MP}], difference in means: -635; 95% confidence interval [CI], -809 to -462; p < 0.001), myoglobin levels (168 +/- 114 [DA] versus 378 +/- 151 [MP], difference in means: -210, 95% CI, -269 to -151; p < 0.001), C-reactive protein (79 +/- 57 [DA] versus 124 +/- 58 [MP], difference in means: -46, 95% CI, -71 to -21; p < 0.001), and interleukin-6 (45 +/- 34 [DA] versus 80 +/- 53 [MP], difference in means: -35, 95% CI, -54 to -16; p < 0.001), but not in other serum markers. In the hospital, patients undergoing the direct anterior approach ambulated 35 steps farther with physical therapy (178 feet DA versus 142 feet MP, p < 0.01, difference in means: 35, 95% CI, 9-62; p = 0.009) and had visual analog scale pain scores 1.1 less (4.8 DA versus 5.9 MP, difference in means: -1.1, 95% CI, 2.0 to -0.2; p = 0.02) than patients undergoing the miniposterior approach. There were no differences between approaches in other in-hospital outcomes or in posthospital clinical milestones. Serum markers including CK, myoglobin, C-reactive protein, interleukin-6, and tumor necrosis factor-alpha did not predict early pain/function after contemporary THA approaches. Although lesser elevations in myoglobin, CK, C-reactive protein, and interleukin-6 were found after direct anterior THA, that difference was not clinically meaningful. Further reporting of serum biomarkers as a measure of physiological burden after orthopaedic surgical procedures should be viewed as suspect until clear linear or threshold values are established. Level III, diagnostic study.