Does the Risk of Death Within 48 Hours of Hip Hemiarthroplasty Differ Between Patients Treated with Cemented and Cementless Implants? A Meta-analysis of Large, National Registries

BACKGROUND: Although current recommendations suggest that hip hemiarthroplasties performed for femoral neck fractures be implanted with bone cement, it is known to cause cardiorespiratory and hemodynamic reactions that in some patients can be fatal. Older patients may be at particular risk of this complication, but because of its relative infrequency, large studies-perhaps even larger than can be achieved in the context of single-country national registries-are needed to get reasonably precise estimates as to its frequency. Pooling results from national registries reporting on death within 48 hours of cement exposure in this setting may therefore be helpful. QUESTION/PURPOSE: In a systematic review of studies based on large national registries, we asked: Does the risk of death within 48 hours of hip hemiarthroplasty differ between patients treated with cemented and cementless implants? METHODS: MEDLINE and Embase data sources were searched for cohort studies on patients with hip fractures treated with cement or cementless hip hemiprostheses based on results from national registries that tracked perioperative deaths within 48 hours of surgery, from 2010 or later (to include only studies that used contemporary cement techniques). We excluded registry research on elective THAs for other indications (such as degenerative joint disease), mixed populations (registries that combined patients having arthroplasty for fracture and for other diagnoses like osteoarthritis, such that we could not separate them), and overlapping data from the same registers (to avoid double and triple publications of similar data). Five studies met our inclusion criteria. The cohorts ranged from about 11,000 to about 25,000 patients. About 31% of the patients were in the cementless group. Two studies reported the age ranges of participating patients, and three studies communicated mean ages (which were 82 years for both sexes). Twice as many females as males were present in both the cemented and cementless group. When reported, more than 50% in both groups were in the American Society of Anesthesiologists physical status classification 3 or 4. Study quality was deemed good according to the Newcastle-Ottawa Scale. Publication bias was assessed using a funnel plot and the Egger test, and study heterogeneity was evaluated using the I2 heterogeneity statistic and Cochran Q heterogeneity test. There was some heterogeneity between the studies, with a Cochran Q statistics of 8.13 (degrees of freedom = 4; p = 0.08) and an I2 statistic of 50.8%. There was evidence for a small amount of publication bias (Egger test; p = 0.02). The pooled risk ratio (RR) from a random-effects model is presented with 95% confidence intervals. The primary endpoint was the occurrence of any fatalities within 48 hours of hip fracture treatment with cementless compared with cemented prostheses. We performed a sensitivity analysis to assess the needed association of a potential unmeasured or uncontrolled confounding, and we made an estimate of the amount of unmeasured confounding that would need to be present in order to change the direction of the result. We summarized this using a parameter known as the "E-value." Based on that sensitivity analysis, we found it unlikely that an unmeasured hypothetical confounder could explain the significant association between cemented and cementless implants and risk of death within 48 hours of hip hemiarthroplasty. RESULTS: Compared with the cementless group, mortality was increased in the cemented group (RR 1.63 [95% CI 1.31 to 2.02]; p < 0.001). The number needed to harm from the pooled data was 1 of 183 operated patients; that is, for every 183 patients treated with cemented implants, one death would be expected. CONCLUSION: Bone cement is associated with a higher risk of fatalities within 48 hours of surgery compared with cementless prostheses. However, numerous prior studies have found a higher risk of serious complications resulting in additional surgical procedures associated with cementless devices in this population; those complications, as well, may result in death. Based on our study alone, we cannot recommend cementless implants in this setting. Large, national registries should evaluate fixation choice in older patients with hip fractures, and those studies should consider both early death and the potential for later harms. LEVEL OF EVIDENCE: Level III, therapeutic study.

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