Greater Medial Compartment Forces During Total Knee Arthroplasty Associated With Improved Patient Satisfaction and Ability to Navigate Stairs.

BACKGROUND: The purpose of this study was to determine if postoperative patient satisfaction, subjective outcomes, and functional force testing differed between those with symmetric or asymmetric intraoperative mediolateral (ML) compressive forces. We hypothesized that the threshold would be similar to the previously reported valued of 15 lbf and that a significantly greater proportion of those with more symmetrical medial and lateral compressive forces would be satisfied with their total knee arthroplasty. METHODS: A commercially available instrumented trial tibial liner was used to measure ML compressive force differences with the knee at 0°, 20°, and 90°. Patient satisfaction and Knee Society Scores were compared between patients with ML asymmetries above and below the calculated optimal threshold. RESULTS: Surprisingly, lower ML asymmetries in extension were associated with a greater risk of being dissatisfied. Of the 50 total knee arthroplasties, 6 of 23 (26%) with ML force asymmetries <10 lbf were dissatisfied compared with 0 of 27 with ML asymmetries >10 lbf (P = .01). Greater asymmetry was associated with significantly greater gains in EQ-5D scores (P = .05) and pain scores (P = .03) and greater pain relief (P = .006) and reduced impact forces when navigating stairs (P = .05). CONCLUSION: Contrary to our hypotheses, the results of this study support the concept that recreating greater forces in the medial compartment much like that of the native knee may yield improved patient-reported outcomes and increased patient satisfaction. The current results further suggest that recreating greater medial compartment forces may have the greatest affect on more demanding activities such as navigating stairs.

An Intact Anterior Cruciate Ligament at the Time of Posterior Cruciate Ligament-Retaining Total Knee Arthroplasty Was Associated With Reduced Patient Satisfaction and Inferior Pain and Stair Function.

BACKGROUND: Patients with an intact anterior cruciate ligament (ACL) at the time of ACL-sacrificing total knee arthroplasty (TKA) have been suggested to have inferior outcomes compared with those with a dysfunctional ACL. However, to date, no published clinical studies have evaluated the potential link between the condition of the ACL at the time of posterior cruciate ligament-retaining TKA and postoperative pain, function, and satisfaction. As such, the purpose of this study was to compare subjective function, movement-elicited pain, pain at rest, and patient satisfaction between those with an intact or dysfunctional ACL. METHODS: We identified 562 posterior cruciate ligament-retaining TKAs with complete intraoperative and postoperative data. Patients were categorized based on the condition of the ACL at the time of TKA as either being intact or dysfunctional (absent or lax). Knee Society Function Scores, movement-elicited pain, pain at rest, and patient satisfaction were then compared between groups. RESULTS: At mean follow-up of 5.1 years, a significantly lower proportion of patients in the intact group were satisfied with their operation (intact: 391/453 [86.3%] vs dysfunctional: 102/109 [93.6%], P = .0496). Inspection of the individual activities revealed that the groups did not differ in walking ability or pain when walking; however, the intact group reported significantly reduced ability to navigate stairs with greater pain during that activity. CONCLUSION: The lack of difference in pain at rest between groups suggests that pain and functional impairments during more demanding activities such as navigating stairs may be associated with the lost function of the ACL rather than by altered central pain processing.

Subchondral Bone Marrow Edema Had Greater Effect on Postoperative Pain After Medial Unicompartmental Knee Arthroplasty Than Total Knee Arthroplasty.

BACKGROUND: Although the relationship between pain and bone marrow edema (BME) in the osteoarthritic knee has been established, little is known about the effect of preoperative BME on postoperative outcomes after knee arthroplasty or if the influence of BME on postoperative outcomes differs between medial unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA). The purpose of this study was to compare pain, patient satisfaction, and revision rates between medial UKA and TKA patients with and without magnetic resonance imaging evidence of BME in the proximal tibia. METHODS: We identified 71 patients (72 knees) from our prospective outcomes database with magnetic resonance images taken before undergoing either medial UKA or TKA and recorded the absence or presence of tibial BME. We then compared preoperative and postoperative Knee Society pain scores, patient satisfaction, and revisions between groups of UKA and TKA patients with or without preoperative tibial BME. RESULTS: Pain scores for UKA patients with BME were worse both before and after surgery, whereas TKA patients with BME demonstrated greater postoperative improvements in pain scores when compared to TKA patients without BME. Similarly, significantly fewer UKA patients with BME were satisfied with their procedure than those without BME (8/11, 73% vs 17/17, 100%; P = .05), but BME did not affect patient satisfaction after TKA. CONCLUSION: Preoperative BME did not influence TKA outcomes; however, pain scores for UKA patients with BME were worse both before and after surgery and fewer UKA patients with preoperative tibial BME were satisfied with their surgery.

Patients with Pain 60 to 120 Days after Total Knee Arthroplasty More Likely to be Dissatisfied at Mid-Term Follow-Up.

The purpose of this study was to determine if TKA patients with pain between 60 and 120 days are more likely to be dissatisfied at mid-term follow-up. At the 60-120 day follow-up, moderate to severe movement-elicited pain (MEP) and pain at rest (PAR) were reported by 25/316 TKAs (7.9%) and 44/316 TKAs (13.9%), respectively. A greater proportion of those with MEP at 60-120 days were dissatisfied at midterm follow-up (24% vs. 6.5%, P = .01), and those with MEP early after surgery were 4.5 times more likely to be dissatisfied at mid-term follow-up (P = .004). Similarly, those with PAR 60-120 days after surgery were 4.1 times more likely to be dissatisfied at mid-term follow-up (P = .002).

Chronic Non-Orthopedic Conditions More Common in Patients with Less Severe Degenerative Changes That Have Elected to Undergo Total Knee Arthroplasty.

The purpose of this study was to determine whether the prevalence of chronic non-orthopedic conditions that may play a role in an abnormal pain response differs between patients based on the severity of degenerative changes at the time of surgery. Of 1020 OA knees that had undergone primary TKA with a minimum 2year follow-up, we identified 117 (11.5%) that had less severe degenerative changes. The prevalence of dissatisfaction was significantly greater in less severe group compared to those with moderate or severe changes (18.8% vs. 9.3%, P=.003). Chronic non-orthopedic conditions were significantly more prevalent in the less severe group with 41.9% reporting depression/anxiety, 30.8% with fibromyalgia or low back pathology, and 12.8% with a prior traumatic brain injury or stroke.

Assessing the utility of routine first annual follow-up visits after primary total knee arthroplasty.

The combination of increased TKA utilization and a decreased number of arthroplasty specialists has resulted in a growing need to maximize efficiency without sacrificing the level of care being provided. The purpose of this study was to evaluate the utility of routine first annual follow-up visits for patients that have undergone primary TKA. Of 339 TKAs performed by a single surgeon in 2012, 23% failed to attend scheduled first annual visits. Furthermore, none of the revisions performed at our facility since 2003 were the direct result of information gained at a patient's routine first annual visit. As such, we question the clinical utility of the first annual visit.

Greater prevalence of wound complications requiring reoperation with direct anterior approach total hip arthroplasty.

The purpose of this retrospective study was to compare wound complication rates between primary THAs performed via a posterior or direct anterior approach. From our prospective outcomes registry, we identified 1288 primary THAs performed via a posterior approach and 505 via a direct anterior approach. The direct anterior approach resulted in a significantly greater number of wound complications that required reoperation than the posterior approach (7/505 (1.4%) vs. 3/1,288 (0.2%), P=0.007). As such, patients should be counseled on the potential increased risk of early wound complications with the direct anterior approach, and future research is needed to determine if alternative closure techniques can reduce the risk of wound complication.

Patient and intraoperative factors influencing satisfaction two to five years after primary total knee arthroplasty.

The purpose of this study was to compare patient demographics and factors recorded at the time of surgery between patients that were either satisfied or dissatisfied with their TKA at mid-term follow-up. From our prospective outcomes database, 989 primary TKAs with complete preoperative and intraoperative data were identified. At mean follow-up of 3.5 years, 94/989 TKAs (9.5%) were not satisfied with their TKA. African American patients were 3.0 times more likely to be dissatisfied than Caucasians (95% CI = 1.5-6.0, P = .003). Patients with less severe degenerative changes were 2.1 times more likely to be dissatisfied (95% CI = 1.3-3.2, P = .001).

Early failures in total hip arthroplasty -- a changing paradigm.

Between 2001 and 2011, 1168 revision hip arthroplasties were reviewed for "early" failures within 5 years of the primary total hip arthroplasty (THA). 24.1% underwent revision within 5 years of index THA. Aseptic loosening, infection, instability, metallosis, and fracture were common modes of failure. In our previous report from 1986 to 2000, 33% were "early" revisions, with instability and aseptic loosening accounting for over 70% of these early failures. While the proportion of "early" revisions decreased 9% from our previous report, this rate remains alarming. The emergence of metallosis and aseptic loosening of monoblock metal on metal shells as leading causes of early failures is concerning. This report suggests caution in the early adoption of new innovations before evidence based medicine is available to justify the risk of their use.

Angiotensin II receptor blockade administered after injury improves muscle regeneration and decreases fibrosis in normal skeletal muscle.

BACKGROUND: Several therapeutic agents have been shown to inhibit fibrosis and improve regeneration after injury in skeletal muscle by antagonizing transforming growth factor-beta1. Angiotensin receptor blockers have been shown to have a similar effect on transforming growth factor-beta1 in a variety of tissues. HYPOTHESIS: Systemic treatment of animals after injury of skeletal muscle with an angiotensin receptor blocker may decrease fibrosis and improve regeneration, mainly through transforming growth factor-beta1 blockade, and can be used to improve skeletal muscle healing after injury. STUDY DESIGN: Controlled laboratory study. METHODS: Forty mice underwent bilateral partial gastrocnemius lacerations. Mice were assigned randomly to a control group (tap water), a low-dose angiotensin receptor blocker group (losartan, 0.05 mg/mL), or a high-dose angiotensin receptor blocker group (0.5 mg/mL). The medication was dissolved in tap water and administered enterally. Mice were sacrificed 3 or 5 weeks after injury, and the lacerated muscles were examined histologically for muscle regeneration and fibrosis. RESULTS: Compared with control mice at 3 and 5 weeks, angiotensin receptor blocker-treated mice exhibited a histologic dose-dependent improvement in muscle regeneration and a measurable reduction in fibrous tissue formation within the area of injury. CONCLUSION: By modulating the response to local and systemic angiotensin II, angiotensin receptor blocker therapy significantly reduced fibrosis and led to an increase in the number of regenerating myofibers in acutely injured skeletal muscle. The clinical implications for this application of angiotensin receptor blockers are potentially far-reaching and include not only sports- and military-related injuries, but also diseases such as the muscular dystrophies and trauma- and surgery-related injury. CLINICAL RELEVANCE: Angiotensin receptor blockers may provide a safe, clinically available treatment for improving healing after skeletal muscle injury.

Regenerative medicine for the musculoskeletal system based on muscle-derived stem cells.

The identification and characterization of stem cells is introducing a paradigm shift in the field of orthopaedic surgery. Whereas in the past, diseased tissue was replaced with allograft material, current trends in research revolve around regenerating damaged tissue. Muscle-derived stem cells have an application in regeneration of articular cartilage, bone, and skeletal muscle. These postnatal (ie, adult) stem cells can be readily isolated via muscle biopsy. They can display long-term proliferation, high self-renewal, and multipotent differentiation. They also can be genetically modified to secrete growth factors important to tissue healing, thereby functioning as implantable, long-lasting reservoirs for these molecules. Taken together, this evidence suggests that muscle-derived stem cells are well suited for gene therapy and tissue engineering applications for the musculoskeletal system. Effective implementation of even just a few applications of muscle-derived stem cell-based tissue engineering has the potential to revolutionize the way certain musculoskeletal diseases are managed.

In vitro microdistraction of preosteoblasts: distraction promotes proliferation and oscillation promotes differentiation.

Osteoblast biology is influenced in vivo by a 3-dimensional (3D) extracellular matrix that mediates their adhesion and interaction and by a constant state of compressive and tensile forces. To study the role of mechanical stress on osteoblasts in vitro, these parameters must be addressed. Therefore, this study describes the use of a novel, in vitro system that subjects cells to distractive and compressive forces in a 3D environment. This system, termed a microdistractor system, was used to apply linear forces to 3D collagen type I gels containing preosteoblasts. Gels were induced for up to 16 days in osteogenic medium and subjected to either constant linear distraction (distraction gels) or to repeating cycles of distraction and compression (oscillation gels). The effect of these stresses was evaluated over time by measuring proliferation rates, protein synthesis (i.e., cellular activity), and osteogenic differentiation levels. While linear forces in general appeared to increase protein synthesis, force-specific effects on proliferation and differentiation were observed. Specifically, distraction forces appeared to enhance MC3T3 proliferation while distraction/compressive forces appeared to accelerate their osteogenic differentiation program. Therefore, these results suggest that the microdistraction system may be an appropriate in vitro system for the study of mechanobiology in osteoblast phenotype.

Origins of highly mosaic mycobacteriophage genomes.

Bacteriophages are the most abundant organisms in the biosphere and play major roles in the ecological balance of microbial life. The genomic sequences of ten newly isolated mycobacteriophages suggest that the bacteriophage population as a whole is amazingly diverse and may represent the largest unexplored reservoir of sequence information in the biosphere. Genomic comparison of these mycobacteriophages contributes to our understanding of the mechanisms of viral evolution and provides compelling evidence for the role of illegitimate recombination in horizontal genetic exchange. The promiscuity of these recombination events results in the inclusion of many unexpected genes including those implicated in mycobacterial latency, the cellular and immune responses to mycobacterial infections, and autoimmune diseases such as human lupus. While the role of phages as vehicles of toxin genes is well established, these observations suggest a much broader involvement of phages in bacterial virulence and the host response to bacterial infections.

Corrected sequence of the bacteriophage p22 genome.

We report the first accurate genome sequence for bacteriophage P22, correcting a 0.14% error rate in previously determined sequences. DNA sequencing technology is now good enough that genomes of important model systems like P22 can be sequenced with essentially 100% accuracy with minimal investment of time and resources.