Effect of Sodium Supplements and Climate on Dysnatremia During Ultramarathon Running.

OBJECTIVE: Analyze the effect of sodium supplementation, hydration, and climate on dysnatremia in ultramarathon runners. DESIGN: Prospective observational study. SETTING: The 2017 80 km (50 mile) stage of the 250 km (150 mile) 6-stage RacingThePlanet ultramarathon in 2017 Chilean, Patagonian, and 2018 Namibian, Mongolian, and Chilean deserts. PARTICIPANTS: All race entrants who could understand English were invited to participate, with 266 runners enrolled, mean age of 43 years (± 9), 61 (36%) females, average weight 74 kg (± 12.5), and average race time 14.5 (± 4.1) hours. Post-race sodium collected on 174 (74%) and 164 (62%) participants with both the blood sample and post-race questionnaire. INTERVENTION: Weight change and finish line serum sodium levels were gathered. MAIN OUTCOME MEASURES: Incidence of exercise-associated hyponatremia (EAH; <135 mmol·L-1) and hypernatremia (>145 mmol·L-1) by sodium ingestion and climate. RESULTS: Eleven (6.3%) runners developed EAH, and 30 (17.2%) developed hypernatremia. Those with EAH were 14 kg heavier at baseline, had significantly less training distances, and averaged 5 to 6 hours longer to cover 50 miles (80 km) than the other participants. Neither rate nor total ingested supplemental sodium was correlated with dysnatremia, without significant differences in drinking behaviors or type of supplement compared with normonatremic runners. Hypernatremic runners were more often dehydrated [8 (28%), -4.7 kg (± 9.8)] than EAH [4 (14%), -1.1 kg (± 3.8)] (P < 0.01), and EAH runners were more frequently overhydrated (6, 67%) than hypernatremia (1, 11%) (P < 0.01). In the 98 (56%) runners from hot races, there was EAH OR = 3.5 [95% confidence interval (CI), 0.9-25.9] and hypernatremia OR = 8.8 (95% CI, 2.9-39.5) compared with cold races. CONCLUSIONS: This was the first study to show that hot race climates are an independent risk factor for EAH and hypernatremia. Sodium supplementation did not prevent EAH nor cause hypernatremia. Longer training distances, lower body mass, and avoidance of overhydration were shown to be the most important factors to prevent EAH and avoidance of dehydration to prevent hypernatremia.

The 2012 John Charnley Award: Clinical multicenter studies of the wear performance of highly crosslinked remelted polyethylene in THA.

BACKGROUND: Highly crosslinked polyethylene (HXLPE) in THA was developed to reduce particle-induced periprosthetic osteolysis. A series of clinical studies were initiated to determine the clinical efficacy as judged by patient-reported scores, radiographic osteolysis, and wear analysis of one form of HXLPE. QUESTIONS/PURPOSES: The purposes of this series of studies were to (1) determine the wear rates of one form of HXLPE; (2) report long-term (7-10 years) patient-reported outcome measures; (3) assess the effect of femoral head size on wear; and (4) determine the incidence of periprosthetic osteolysis. METHODS: A single-center and two multicenter studies were conducted on 768 primary patients (head size 26-36 mm) undergoing THA at eight medical centers. Patient-reported outcome scores, radiographic grading for osteolysis, and radiographic wear evaluation were performed. RESULTS: Serial plain radiographs showed no periprosthetic osteolysis in the three studies. The average femoral head penetration rates did not correlate with time in vivo for patients with standard femoral head sizes. Although there was an indication of higher wear in patients with 36-mm diameter femoral heads, it was below the threshold for producing osteolysis. CONCLUSIONS: The introduction of this HXLPE substantially improved the prognosis of patients after THA up to 13 years as judged by clinical scores, incidence of osteolysis, and polyethylene wear measurements. LEVEL OF EVIDENCE: Level III, therapeutic study. See the Guideline for Authors for a complete description of levels of evidence.

What factors influence long-term survivorship after hip arthroscopy?

BACKGROUND: Hip arthroscopy is an evolving procedure. One small study suggested that a low modified Harris hip score and arthritis at the time of surgery were predictors of poor prognosis. QUESTIONS/PURPOSES: We therefore intended to confirm those findings with a large patient cohort to (1) determine the long-term nonarthritic hip score; (2) determine survivorship; (3) identify risk factors that increase the likelihood of THA; and (4) use those factors to create a usable risk assessment algorithm. PATIENTS AND METHODS: We retrospectively reviewed 324 patients (340 hips) who underwent arthroscopy for pain and/or catching. Of these, 106 patients (111 hips or 33%) had a minimum followup of 10 years (mean, 13 years; range, 10-20 years). The average age was 39 years (± 13) with 47 men and 59 women. We recorded patient age, gender, acetabular and femoral Outerbridge grade at surgery, and the presence of a labral tear. Followup consisted of a nonarthritic hip score or the date of a subsequent THA. We determined survivorship with the end point of THA for the acetabular and femoral Outerbridge grades. RESULTS: Overall survivorship among the 111 hips was 63% at 10 years. The average nonarthritic hip score for non-THA patients was 87.3 (± 12.1). Survivorship was greater for acetabular and femoral Outerbridge grades normal through II. Age at arthroscopy and Outerbridge grades independently predicted eventual THA. Gender and the presence of a labral tear did not influence long-term survivorship. CONCLUSIONS: The long-term survivorship of labral tears with low-grade cartilage damage indicates hip arthroscopy is reasonable for treating labral tears. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

The John Charnley Award: risk factors for cup malpositioning: quality improvement through a joint registry at a tertiary hospital.

BACKGROUND: Few studies have examined factors that affect acetabular cup positioning. Since cup positioning has been linked to dislocation and increased bearing surface wear, these factors affecting cup position are important considerations. QUESTION/PURPOSES: We determined the percent of optimally positioned acetabular cups and whether patient and surgical factors affected acetabular component position. METHODS: We obtained postoperative AP pelvis and cross-table lateral radiographs on 2061 consecutive patients who received a THA or hip resurfacing from 2004 to 2008. One thousand nine hundred and fifty-two hips had AP pelvic radiographs with correct position of the hip center, and 1823 had both version and abduction angles measured. The AP radiograph was measured using Hip Analysis Suite™ to calculate the cup inclination and version angles, using the lateral film to determine version direction. Acceptable ranges were defined for abduction (30°-45°) and version (5°-25°). RESULTS: From the 1823 hips, 1144 (63%) acetabular cups were within the abduction range, 1441 (79%) were within the version range, and 917 (50%) were within the range for both. Surgical approach, surgeon volume, and obesity (body mass index > 30) independently predicted malpositioned cups. Comparison of low versus high volume surgeons, minimally invasive surgical versus posterolateral approach, and obesity versus all other body mass index groups showed a twofold (1.5-2.8), sixfold (3.5-10.7), and 1.3-fold (1.1-1.7) increased risk for malpositioned cups, respectively. CONCLUSIONS: Factors correlated to malpositioned cups included surgical approach, surgeon volume, and body mass index with increased risk of malpositioning for minimally invasive surgical approach, low volume surgeons, and obese patients. Further analyses on patient and surgical factors' influence on cup position at a lower volume medical center would provide a valuable comparison. LEVEL OF EVIDENCE: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

In vivo biological response to vitamin E and vitamin-E-doped polyethylene.

BACKGROUND: Cross-linking has decreased the wear of ultra-high molecular weight polyethylene, a cause of osteolysis leading to total joint replacement failure. Compared with melting or annealing, doping cross-linked ultra-high molecular weight polyethylene with vitamin E stabilizes free radicals from irradiation while maintaining mechanical properties and wear resistance. This study was done to determine the local tissue effects of free vitamin E and vitamin E eluted from ultra-high molecular weight polyethylene implants in the joint space. METHODS: Three studies were performed. First, pure vitamin E and solubilized vitamin E were injected into rabbit knees to simulate vitamin-E elution from radiation cross-linked ultra-high molecular weight polyethylene; second, vitamin-E-doped, irradiated ultra-high molecular weight polyethylene plugs were implanted into dorsal subcutaneous pouches of rabbits to determine the local effects of vitamin-E elution from radiation cross-linked ultra-high molecular weight polyethylene; and, third, two groups of vitamin-E-doped, irradiated acetabular liners (high surface and uniform vitamin-E concentration profiles) were compared with undoped, control ultra-high molecular weight polyethylene liners in a canine model of total hip replacement to determine the effect of possible vitamin-E elution on bone ingrowth and the local tissue response to it in a load-bearing environment. RESULTS: Injection of solubilized vitamin E resulted in histologically normal surrounding soft tissue at both two and twelve-week follow-up intervals, while injection of pure vitamin E resulted in acute and chronic inflammation at the time of the two-week follow-up. Both control and vitamin-E-doped subcutaneous plugs showed inflammation associated with surgery at two weeks of follow-up, but showed stable fibrous encapsulation without inflammation at twelve weeks of follow-up. In the canine total hip replacement model, there was no qualitative difference in local tissue appearance and no significant difference in the percent bone ingrowth and the percent bone density between the control and vitamin-E groups. CONCLUSIONS: These investigations showed that vitamin-E-doped ultra-high molecular weight polyethylene plugs and total hip replacement components are well tolerated in both a small and a large-animal model with no observed adverse effects on the surrounding tissues at twelve weeks of follow-up.