AAOS Now

Published 8/1/2018

Second Look—Clinical

Hip and Knee

BMI and mortality—Underweight patients undergoing total hip arthroplasty (THA) or total knee arthroplasty (TKA) may have increased all-cause mortality, but this was not the case for overweight and obese patients, according to a study published in Clinical Orthopaedics and Related Research (June). Researchers used data from the Australian St. Vincent’s Melbourne Arthroplasty Outcomes Registry and the U.S. Kaiser Permanente Total Joint Replacement Registry. They identified adult patients undergoing elective TKAs and THAs between Jan. 1, 2002, and Dec. 31, 2013. In both cohorts, being underweight (body mass index [BMI] < 18.5 kg/m2) was associated with higher all-cause mortality after TKA, whereas obese class I (BMI 30.0–34.9 kg/m2) and obese class II (BMI 35.0–39.9 kg/m2) were associated with lower mortality compared to normal-weight patients (BMI 18.5–24.9 kg/m2). In the United States, being underweight had a higher risk of mortality after THA, whereas overweight (25.0–29.9 kg/m2), obese class I, and obese class II individuals had a lower risk of mortality after THA compared to normal-weight patients. In the Australian cohort, there was no observed association between BMI and mortality for patients undergoing THA.

Cost of THA—Despite industry interest in improving price transparency, a study published in JAMA (online) found no evidence of this between 2012 and 2016 among THAs at 120 hospitals. Researchers surveyed the group of hospitals in 2011 and again in 2016 to see whether there was a change in price reporting for THAs. Investigators called each hospital posing as a granddaughter seeking information on the cost of a primary hip replacement for her 62-year-old grandmother, specifically looking for the lowest “cash” bundled price. Only eight hospitals (6.7 percent) gave a bundled price; 20.8 percent (n = 25) provided a complete price, 28.3 percent (n = 34) provided a partial price, and 44.2 percent (n = 53) could not provide any pricing information. The percentage of hospitals able to provide a bundled price declined from 15.8 percent in 2012 to 6.7 percent in 2016. The mean bundled/complete price did not change significantly—it was $44,300 in 2012 and $37,900 in 2016.

In-office diagnostic arthro-scopy—In-office needle-based diagnostic imaging appears to be statistically equivalent to surgical diagnostic arthroscopy in patients with knee pain, according to an article published in Arthroscopy (online). The prospective, blinded, multicenter trial included 110 consecutive patients aged 18–75 years who presented with knee pain between April 2012 and April 2013. Each patient underwent a physical examination, MRI, in-office diagnostic imaging, and a diagnostic arthroscopic examination in the operating room. Two blinded, unaffiliated experts reviewed the in-office arthroscopic images and MRI images using the surgical diagnostic arthroscopy images as the “control” group. The accuracy, sensitivity, and specificity of in-office arthroscopy were equivalent to that of surgical diagnostic arthroscopy and more accurate than that of MRI. No patient- or device-related complications were associated with in-office arthroscopy.

TKA mortality—A study published in The Journal of Bone & Joint Surgery (JBJS; June 20) observed an ongoing worldwide temporal decline in mortality following TKA, which researchers said may be due to improved patient selection and perioperative care and a healthy population effect. Researchers conducted a literature review of MEDLINE, AMED, CAB Abstracts, and Embase to identify 37 studies published between 2006 and 2016 that reported on 30- or 90-day mortality following TKA. The selected studies represented 1.75 million TKAs performed in 15 countries. Thirty- and 90-day mortality was 0.20 percent and 0.39 percent, respectively, both of which decreased during the 10-year study period. By 2015, 30-day mortality following TKA decreased to 0.10 percent, and 90-day mortality decreased to 0.19 percent. The leading cause of death was cardiovascular disease.

Hip dysplasia—A retrospective cohort study published in The Bone & Joint Journal (online) shows that one in five children who undergo treatment of developmental dysplasia of the hip with medially approached open reduction may experience poor outcomes. The study included 52 children (58 hips) aged younger than 1 year at the time of surgery. Radiographs were assessed preoperatively, as well as at one and five years postoperatively and at a mean 12.7 years (range, 4.6–20.8 years) postoperatively. Researchers found that 11 hips (19 percent) showed signs of avascular necrosis, 13 hips (22 percent) needed further surgery, and 13 hips showed poor radiological outcome (defined as Severin type 3 or higher). Patients whose hips showed poor radiological outcomes were significantly older at the time of surgery than patients whose hips had a good Severin classification (1 or 2).

Intravenous versus topical TXA—Intravenous (IV) and topical tranexamic acid (TXA) in patients undergoing TKA are both effective in reducing perioperative bleeding, according to a study published in JBJS (June 20). Researchers randomized 640 patients who underwent unilateral TKA for osteoarthritis at two large academic centers to receive 1 g of IV TXA before tourniquet application and 1 g at closure, or 3 g of TXA diluted in 45 mL of saline and topically applied following cementation. Researchers found that blood loss and drain output were significantly greater in patients who received topical TXA compared to those who received IV TXA, although they said the differences may not be clinically important. Rates of transfusion and thrombotic events were not significant in either group.

Redislocation of LPD—A study published in The American Journal of Sports Medicine (online) appears to show that surgical repair of a medial patellofemoral ligament (MPFL) injury in the acute phase in skeletally immature children with a primary traumatic lateral patellar dislocation (LPD) significantly reduced the redislocation rate but did not improve subjective or objective knee function compared to a knee brace without repair. The prospective series followed 74 patients (mean age, 13.1 years) with a first-time traumatic LPD who underwent clinical examinations, radiographs, MRI, and diagnostic arthroscopic surgery within two weeks of the index injury. Children were randomized to receive a knee brace for four weeks and physical therapy, or arthroscopic-assisted repair of the MPFL with anchors, four weeks with a soft cast splint, and physical therapy. After two years of follow-up, the redislocation rate was significantly lower in the arthroscopic-assisted repair group (n = 8, 22 percent) versus the knee brace group (n = 16, 43 percent). However, most patients in both cohorts were reportedly satisfied with knee function. Researchers said there was a high representation of anatomic patellar instability risk factors in the cohort, which surgeons should consider when evaluating the risk of redislocations.

Biomarkers for osteolysis—Biomarkers may be predictive of osteolysis risk in patients undergoing total hip replacement (THR), according to a study published in the Journal of Orthopaedic Research (online). Using 24-hour urine samples taken from 26 THR patients between 1989 and 1997—16 of whom contracted osteolysis—researchers examined biomarkers at radiographic diagnosis, annually for six years prior to diagnosis, at the first postoperative sampling point, and preoperatively. Of the seven candidate biomarkers observed, free deoxypyridinoline correlated most strongly with the occurrence of osteolysis as an individual biomarker, with an area under the curve (AUC) in receiver operating characteristic analyses
of 0.844 at six years prior to
diagnosis. A panel containing connective tissue protein alpha CTX and interleukin-6 identified patients at risk of osteolysis with an AUC > 0.941 at all postoperative measurements and an AUC of 1.0 preoperatively.

Hip fracture management—According to a study published in JAMA (online), surgically repairing hip fractures in nursing home residents with advanced dementia may be associated with decreased mortality rates. Researchers conducted a retrospective cohort study and identified 3,083 patients (average age, 84 years; 79.2 percent female) who met inclusion criteria using nationwide Medicare claims data linked with Minimum Data Set assessments from Jan. 1, 2008, through Dec. 31, 2013. Overall, 2,615 patients (84.8 percent) received surgery. At six-month follow-up, 824 (31.5 percent) of the surgically and 252 (53.8 percent) of the nonsurgically managed patients died, indicating that surgically managed patients were less likely to die (adjusted hazard ratio, 0.88; 95 percent confidence interval, 0.79–0.98). Of the 2,007 patients who were alive at six months, those who underwent surgery experienced slightly less pain than those who did not (29 percent versus 30.9 percent); however, the prevalence of pain in both cohorts suggests the need for improvements in care, according to the investigators.