Number of knee replacements soars since 1990s
The United States has seen a run on total knee arthroplasty (TKA) procedures during the past 2 decades, a new study shows. The annual primary volume of TKA procedures increased 162%, from 93,230 to 243,802, between 1991 and 2010. Per capita utilization increased 99% (from 31.2 procedures per 10,000 Medicare enrollees in 1991 to 62.1 procedures per 10,000 in 2010).
Investigators conducted an observational study involving more than 3.2 million Medicare patients who underwent primary TKA or revision TKA. Researchers analyzed changes in primary and revision TKA volume, per capita utilization, hospital length of stay (LOS), readmission rates, and adverse outcomes.
In addition to the increase in primary TKA procedures, revision TKA increased by 106% during the 2 decades studied (from 9650 to 19,871). Per capita TKA revisions increased 59% (from 3.2 procedures per 10,000 Medicare enrollees in 1991 to 5.1 procedures per 10,000 in 2010).
For primary TKA, hospital LOS decreased from 7.9 days between 1991 and 1994 to 3.5 days between 2007 and 2010. From 1991 to 2010, rates of adverse outcomes resulting in readmission remained stable for primary TKA, but rates of all-cause 30-day readmission increased from 4.2% to 5.0%. For revision TKA, the decrease in hospital LOS was accompanied by an increase in rate of all-cause 30-day readmission, from 6.1% to 8.9%, and an increase in rate of readmission for wound infection, from 1.4% to 3.0%.
Investigators also documented that greater numbers of obese and diabetic patients undergo TKA these days. In addition, more patients receive outpatient rehabilitation today compared with 2 decades ago.
Investigators credit the increased volume of TKA procedures, in part, to the large number of aging baby boomers. High success rates with the surgery may spur a larger proportion of that aging population to elect to have the procedure.
Source: Cram P, Lu X, Kates SL, Singh JA, Li Y, et al. Total knee arthroplasty volume, utilization, and outcomes among Medicare beneficiaries, 1991-2010. JAMA. 2012;308(12):1227-1236.
Uncovering the risks for infection after spinal surgery
Investigators set out to identify the independent risk factors for development of a surgical site infection (SSI) after spinal surgery. Although not conclusive, strong evidence suggests that 6 factors are related to SSI among patients who undergo spinal surgery.
Investigators evaluated 36 observational studies involving 2439 patients with SSI after spinal surgery. The studies covered a range of indications and surgical procedures and were published between 1998 and 2012.
In total, 46 independent factors were evaluated for risk of SSI. There was strong evidence for 6 factors: 1) obesity/body mass index; 2) longer operation times; 3) diabetes, 4) smoking; 5) history of previous SSI; and 6) type of surgical procedure.
Although there is no conclusive evidence for why postoperative SSI occurs, these findings can help guide clinicians to choose an optimal prophylactic strategy, depending on patient factors. Further research is required to evaluate the effects of these risk factors fully.
Source: Xing D, Ma JX, Ma XL, Song DH, Wang J, et al. A methodological, systematic review of evidence-based independent risk factors for surgical site infections after spinal surgery. Eur Spine J. 2012;Sep 22. [Epub ahead of print]
Accuracy of frozen section histopathologic analysis vs. microbiologic cultures
Investigators conducted a study to determine the accuracy of intraoperative frozen-section histopathologic analysis to diagnose periprosthetic joint infection. Intraoperative frozen sections of periprosthetic tissues performed well in predicting a diagnosis of culture-positive periprosthetic joint infection, but they were only moderately accurate in excluding this diagnosis.
Investigators conducted a systematic review and meta-analysis of studies that compared histologic results of frozen sections with microbiologic cultures obtained at the same time during revision total hip or total knee arthroplasty. Twenty-six studies involving 3269 patients who underwent revision hip or knee arthroplasty met the inclusion criteria. In all, 796 (24.3%) of the patients had a culture-positive periprosthetic joint infection.
No significant difference was noted in the diagnostic accuracy of microbiologic cultures and frozen section histopathologic analysis using common thresholds of 5 or 10 polymorphonuclear leukocytes (PMN) per high-power field. Based on results, investigators recommended that frozen section histopathologic analysis be considered a valuable part of the diagnostic work-up for patients scheduled for revision arthroplasty. The optimal diagnostic threshold (number of PMN per high-power field) required to distinguish periprosthetic joint infection from aseptic failure could not be discerned.
Source: Tsaras G, Maduka-Ezeh A, Inwards CY, Mabry T, Erwin PJ, et al. Utility of intraoperative frozen section histopathology in the diagnosis of periprosthetic joint infection: a systematic review and meta-analysis. J Bone Joint Surg Am. 2012;94(18):1700-1711.
Osteoarthritis of the knee: linking tissue abnormalities with physical findings
In patients with osteoarthritis of the knee, biomechanical factors and physical examination findings are associated with tissue abnormalities, according to evidence obtained via conventional radiography and high-resolution 3.0-T MRI.
In a study involving 105 patients with osteoarthritis, quadriceps weakness was associated with cartilage integrity, effusion, and synovitis (all detected with MRI), and joint space narrowing detected with conventional radiography (CR). Knee joint laxity was associated with MRI-detected cartilage integrity, CR-detected joint space narrowing, and osteophyte formation. Multiple tissue abnormalities detected with MRI, including cartilage integrity, osteophytes, and effusion, were associated with physical examination findings such as crepitus.
Investigators observed a significant association between quadriceps weakness and both effusion and synovitis, as detected with MRI. Inflammation was detected in more than one third of patients, which emphasizes the inflammatory component of osteoarthritis and the potential importance of anti-inflammatory therapies in knee osteoarthritis.
Source: Knoop J, Dekker J, Klein JP, et al. Biomechanical factors and physical examination findings in osteoarthritis of the knee: associations with tissue abnormalities assessed by conventional radiography and high resolution 3.0 Tesla magnetic resonance imaging. Arthritis Res Ther. 2012 Oct 5;14(5):R212. [Epub ahead of print]
Does total hip arthroplasty change pelvic tilt?
How great is the variation in pelvic tilt after total hip arthroplasty (THA)? It is less than 2 degrees on average, new data show.
Investigators measured the variation in pelvic tilt in 30 patients before THA and the effect of THA on pelvic tilt in the same patients more than a year after surgery. A CT scan was obtained in each patient, for CT-based surgical navigation, as were preoperative and postoperative standing and supine radiographs. Each of the radiographs was used to calculate pelvic tilt via a novel and validated 2-dimensional/3-dimensional matching technique.
Average supine pelvic tilt changed less than 2 degrees, from 4.4 ± 6.4 degrees before THA to 6.3 ± 6.6 degrees after THA. Average standing pelvic tilt changed less than 1 degree, from 1.5 ± 7.2 degrees before THA to 2.0 ± 8.3 degrees after THA. Preoperative pelvic tilt correlated with postoperative tilt in both supine and standing positions.
Source: Murphy WS, Klingenstein G, Murphy SB, Zheng G. Pelvic tilt is minimally changed by total hip arthroplasty. Clin Orthop Relat Res. 2012 Sep 22. [Epub ahead of print]
Use of anticoagulants too frequent after orthopaedic surgery?
Although orthopaedic patients are at high risk for pulmonary embolism, results of a study suggest that pulmonary embolism may be overdiagnosed. The investigators recommend that clinicians evaluate the nature of a clinically relevant pulmonary embolism and assess the timing, risks, and outcomes of therapeutic anticoagulation in surgical patients.
Recent literature shows the incidence of pulmonary embolism to be increasing without a corresponding increase in mortality. This finding may suggest that increasingly sensitive tests may be picking up small emboli. The size and location of a clot or clots may affect therapy decisions. A risk-benefit evaluation can be helpful in deciding on a course of treatment.
Although there is no consensus regarding optimal treatment for patients with pulmonary embolism, investigators say the results of recent studies indicate that physicians who treat orthopaedic surgery and trauma patients may need to use broader criteria to screen for potentially dangerous clots before beginning anticoagulant therapy. Future studies may provide the information to develop guidelines for treating orthopaedic patients with small clots.
Sources: Tornetta P, Bogdan Y. Pulmonary embolism in orthopaedic patients: diagnosis and management. J Am Acad Orthop Surg. 201; 20:586-595. American Academy of Orthopaedic Surgeons. Anti-clotting therapy may be used too often following orthopaedic surgery or trauma.
[press release]. September 1, 2012.
Managing shoulder dislocation in older patients
Treating shoulder dislocation poses different diagnostic and treatment challenges in older patients than in younger patients, according to a new study that analyzes these differences and suggests a way to evaluate older patients that could help improve diagnosis and management of interrelated injuries. Approximately 20% of all shoulder dislocations occur in patients age 60 years and older. Although shoulder dislocation can occur at about the same rates in both younger and older patients, injuries in older patients are more likely to be overlooked or misdiagnosed, resulting in years of persistent pain and disability.
Older patients who sustain a primary shoulder dislocation are much less likely than younger patients to have a recurrence, but they are more likely to sustain injuries to the rotator cuff, axillary nerve, or brachial plexus. In older patients, the incidence of rotator cuff tears in shoulder dislocation ranges from 35% to 86%.
Concomitant injuries, especially of the rotator cuff, often are missed or mistaken for nerve palsies. Older patients with persistent shoulder pain and dysfunction after dislocation should be evaluated carefully for rotator cuff pathologic processes. Today, older patients are much more active than patients in the same age group were a decade ago. Careful evaluation of all shoulder injuries in older patients is important to avoid injury mismanagement.
Sources: Murthi AM, Ramirez MA. Shoulder dislocation in the older patient. J Am Acad Orthop Surg. 2012;20(10):615-622. American Academy of Orthopaedic Surgeons. Shoulder dislocation in older patients poses different challenges in diagnosis, treatment [press release]. October 4, 2012.
The skeleton . . . as an endocrine organ?
Surprising discoveries in the field of skeletal biology suggest that bone cells produce endocrine hormones that regulate phosphate and glucose homeostasis. In a new report, investigators describe the features of these new endocrine pathways and consider their physiologic importance in the context of energy metabolism and mineral homeostasis.
Consideration of research in evolutionary and comparative biology suggests that a driving force for the emergence of these hormonal pathways was the development of a large, energy-expensive musculoskeletal system. Specialized bone cells also evolved and produced endocrine hormones to integrate the skeleton in global mineral and nutrient homeostasis.
The recognition of bone as a true endocrine organ offers a fertile area for further research. This area of study could improve diagnosis and treatment of metabolic diseases, including osteoporosis and diabetes mellitus.
Source: Digirolamo DJ, Clemens TL, Kousteni S. The skeleton as an endocrine organ. Nat Rev Rheumatol. 2012;Oct 9. doi: 10.1038/nrrheum.2012.157. [Epub ahead of print]
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