In the January 4, 2017 issue of The Journal, Swart et al. provide a well-done Markov decision analysis on the cost effectiveness of three treatment options for femoral neck fractures in patients between the age of 40 and 65: open reduction and internal fixation (ORIF), total hip arthroplasty (THA), and hemiarthroplasty. Plugging the best data available from the current orthopaedic literature into their model, the authors estimated the threshold age above which THA would be the superior strategy in this relatively young population.
For patients in this age group, traditional thinking has been to perform ORIF in order to “save” the patient’s native hip and avoid the likelihood of later revision arthroplasty. However, in this analysis THA emerges as a cost-effective option in otherwise healthy patients >54 years old, in patients >47 years old with mild comorbidity, and in patients >44 years old with multiple comorbidities.
On average, both THA and ORIF have similar outcomes across the age range analyzed. But ORIF with successful fracture healing yields slightly better outcomes and considerably lower costs than THA, whereas patients whose fracture does not heal with ORIF have notably worse outcomes than THA patients. This finding supports my personal bias that anatomical reduction and biomechanically sound fixation must be achieved in this younger population with displaced femoral neck fractures. The analysis confirmed that, because of poor functional outcomes with hemiarthroplasty in this population, hemiarthroplasty should not be considered. Poor hemiarthroplasty outcomes are likely related to the mismatch between the metal femoral head and the native acetabular cartilage, leading to fairly rapid loss of the articular cartilage and subsequent need for revision.
This analysis by Swart et al. provides very valuable data to discuss with younger patients and families when engaging in shared decision making about treating an acute femoral neck fracture. In my experience, most patients in this age group prefer to “keep” their own hip whenever possible, which puts the onus on the surgeon to gain anatomic reduction and biomechanically sound fixation with ORIF.
Marc Swiontkowski, MD
Total hip arthroplasty made its debut about 60 years ago. As with most new technologies, it was anticipated that advances and improvements would occur. However, the improvements have been incremental and in some cases have led to problems, particularly with regard to interchangeable parts, modularity, and the materials used for articulating surfaces. Some still believe that total hip arthroplasty was close to being optimized at the time that it was introduced.
Some may view these comments as somewhat provocative, but I would not be surprised if a lot of surgeons agree. The issue of trunnion wear is one example of these problems. One of the main contributing factors is the fact that each implant manufacturer uses tapers with their own specifications, which vary in terms of angle, diameter, straightness, roundness, and surface properties. Therefore, most femoral neck implant tapers are not necessarily compatible with each other. It is important to note that femoral heads should not be used interchangeably between designs as the cone angle may differ. ?If this is done, trunnionosis will be a likely outcome.
In the August 2016 issue of JBJS Reviews, Lanting et al. provide an important and very worthwhile discussion of the risk factors for trunnionosis. Trunnionosis may be enabled by the disruption of the protective oxidative layer on the metal by fretting, potentiating the corrosion of the exposed metal beneath the oxidative layer through an active combination of biochemical and electrochemical processes. Time in vivo consistently has been shown to be a risk factor for trunnionosis. Flexural rigidity of the trunnion has been demonstrated to have an important role in the development of trunnionosis. A flexible trunnion may allow fretting as well as point loading. Edge loading is known to make tribocorrosion more likely to occur. In the presence of any degree of angular mismatch, the effect of trunnionosis may be increased.
The role of design and manufacturing variables in the development of trunnion problems continues to be debated. Surgeon-related factors, especially the greater variability and taper assembly with smaller-incision surgery, also may contribute to this phenomenon. Patients presenting with unexplained pain who have modular neck-body implants should be considered to have an adverse local tissue reaction resulting from corrosion of the neck-stem interface as potential cause of the pain.
In most cases, I suspect that removal of the femoral head, cleaning of the taper, and replacement with a different femoral head (usually a ceramic head with a titanium adapter sleeve) represents adequate treatment based on care recommendations. In contrast, in cases involving adverse local tissue reactions associated with the modular neck designs, removal of the modular stem and neck may be required.
Thomas A. Einhorn, MD
Editor, JBJS Reviews
Obesity can negatively affect outcomes after total hip arthroplasty (THA), and an inadvertent reduction in cup anteversion may be one reason why, according to findings from Brodt et al. in the May 4, 2016 edition of The Journal of Bone & Joint Surgery.
The authors retrospectively analyzed postoperative radiographs from 790 THA patients (all of whom were operated on via a direct lateral approach) within three BMI ranges: normal weight (BMI <25 kg/m2), moderately obese (BMI between 25 and 34 kg/m2), and morbidly obese (BMI of ≥35 kg/m2). Reduced cup anteversion significantly correlated with increasing BMI and younger patient age, with the morbidly obese group demonstrating a 3.4° anteversion reduction compared with the normal-weight group. The authors attribute the reduced anteversion to increased pressure applied to dorsal and ventral acetabular rim retractors to ensure adequate visualization during THA surgery in obese patients.
When the authors applied their findings to the Lewinnek “safe zone” for acetabular positioning, only 59% of the morbidly obese patients were in that zone. While this study was not designed to track subsequent dislocations (a common consequence of incorrect cup positioning), the authors claim that these findings are nevertheless clinically important. “Knowledge of a systemic error in obese patients should raise surgeons’ awareness of the need to perform cup implantation with greater attention,” they conclude.
Obesity is one of the most serious public health problems in the 21st century, and body weight is becoming an important consideration in orthopaedic procedures, especially joint arthroplasty. Two new studies in the February 3, 2016 Journal of Bone & Joint Surgery illuminate the relationship between body mass index (BMI) and hip-arthroplasty outcomes.
In a prognostic study based on registry data (21,361 consecutive hip replacements), Wagner et al. analyzed postsurgical complications and reoperations using BMI as a continuous variable. They found strong associations between increasing BMI and increasing rates of reoperation, implant revision or removal, early hip dislocation, and both superficial and deep infections. Although researchers are just starting to examine the efficacy of preoperative interventions to reduce BMI (see related OrthoBuzz post), Wagner et al. suggest that “collaborative interventions between care providers and patients may be undertaken to modify risk factors, such as BMI, before elective procedures.” A commentary on this study lauds the authors for analyzing BMI with a “dose-response” perspective, but the commentators note that “BMI neither remains constant nor follows a predictable trend over time.”
In a separate therapeutic study by Issa et al., clinical and patient-reported outcomes of primary THA were lower in super-obese patients (BMI ≥ 50 kg/m2) than in matched patients with normal BMI (<30 kg/m2). Specifically, after a mean follow-up of six years, compared with the normal-BMI group, the super-obese group had:
- A 4.5 times higher odds ratio (OR) of undergoing a revision
- A 7.7 times higher OR of surgical complications, including superficial and deep infections
- Significantly lower mean values on the Harris hip score, the physical and mental components of the SF-36, and the UCLA activity score.
Despite these between-group findings, super-obese patients still experienced significant clinical improvements compared with their preoperative status. However, they saw an average of 2.5 previous surgeons who refused to perform the procedure prior to being referred to the authors.
When it comes to acetabular cup positioning during total hip arthroplasty (THA), precision really matters. Malpositioned cups increase the risk of dislocation, early wear, and loosening, among other unwanted outcomes.
In the January 20, 2016 issue of The Journal of Bone & Joint Surgery, Sariali et al. report on results of a randomized trial that compared cup positioning guided by three-dimensional (3-D) visualization tools used intraoperatively (28 patients) with freehand cup placement (28 patients). Cup anteversion was more accurate in the 3-D planning group, and the percentage of anteversion outliers according to the Lewinnek safe zone was lower in the 3-D planning group. Although cup abduction was restored with greater accuracy in the 3-D planning group, the percentage of abduction outliers was comparable between groups.
Interestingly, operative times did not differ between the two groups. The authors note that CT-based navigation, a more expensive technology used to improve acetabular-cup positioning, does increase operative times, although its reported accuracy is higher than that of the 3-D planning technique used in this trial. That apparent tradeoff leads the authors to conclude that “3-D planning may be a good compromise between accuracy on the one hand and extra cost and duration of surgery on the other hand.”
It should also be noted that Sariali et al. did not measure clinical outcomes in this study, so there’s no evidence here that the accuracy enhancements arising from 3-D planning translate into meaningful clinical improvements.
All you stats geeks out there will love the January 6, 2016 study in The Journal of Bone & Joint Surgery by Schilling and Bozic. We at OrthoBuzz are going to skip the gory statistical details for the most part and focus on the essential findings.
First the premise and purpose of the study: Because measuring and improving health care outcomes are nowadays top priorities, risk adjustment—methods to account for differences in patient characteristics across providers—has become a contentious issue. General risk-assessment models tend not to be well-tailored to orthopaedic procedures. So Schilling and Bozic developed a series of risk-adjustment models specific to 30-day morbidity and mortality following hip fracture repair (HFR), total hip arthroplasty (THA), and total knee arthroplasty (TKA). To develop their models, they used prospectively collected clinical data from the National Surgical Quality Improvement Program.
Here are the major findings: For THA and TKA, risk-adjustment models using age, sex, and American Society of Anesthesiologists (ASA) physical status classification were nearly as predictive as models using many additional covariates. HFR model discrimination improved with the addition of comorbidities and laboratory values. Vital signs did not improve model discrimination for any of the procedures.
The study confirms that it is possible to provide adequate risk adjustment for analyzing outcomes of these procedures using only a handful of the most predictive variables commonly available within the operative record. “More parsimonious models are a viable alternative when the adequacy of risk adjustment must be weighed against the cost and burden of large-scale data extraction from the clinical record,” the authors conclude.
Ceramic hip components are often chosen for younger patients to minimize long-term wear. Ceramic femoral head fractures arise mainly from trauma; non-compatible, damaged, or contaminated femoral head/stem taper connections; or material or manufacturing defects.
Because ceramic head fractures are more likely to occur from insults during or after implantation than from manufacturing defects, the Watch includes four “golden rules” surgeons can follow to reduce the risk of these events, including making sure that the tapers on both the head and stem are compatible in all dimensions. The Watch also emphasizes the importance of patient education, during which patients should be encouraged to promptly report any and all postsurgical irregularities.