Porous Tantalum Buttress Augments for Severe Acetabular Posterior Column Deficiency

In revision total hip arthroplasty (THA), consensus is lacking regarding the optimal method for reconstruction of the most severe acetabular defects. Porous tantalum (TM) buttress augments were designed for the most severe postero-superior defects. The purpose of this study was to report the results of a consecutive series of acetabular reconstructions utilizing TM buttress augments. Eight complex acetabular reconstructions utilizing a TM buttress augment were performed at two centers. All were Paprosky 3A or Paprosky 3B bone loss classification, with severe superior and posterior column deficiency where wedge augments were insufficient for mechanical support. The acetabular cup sizes ranged from 64-78, and a buttress shim was used in 7 of 8 cases. Clinical and radiographic follow-up averaged 16.5 months (range, 10-28) and no cases were lost to follow-up. There were no cases of clinical or radiographic loosening, and no case had required reoperation or revision. All patients except one were ambulating with either no assist device or a single cane at final follow-up. There was one complication of an iliac wing fracture noted incidentally on postoperative x-rays in the lone patient in whom a buttress shim was not used. At short-term follow-up, TM acetabular buttress augments appear to effectively substitute for the use of structural allografts or cages, which would otherwise be used in this challenging setting. The potential for biologic fixation is promising for the durability of these reconstructions; however, longer-term follow-up is required for full evaluation.

Hip contact stress and femoral neck retroversion: a biomechanical study to evaluate implication of femoroacetabular impingement

The current literature on femoroacetabular impingement (FAI) is focused on acetabular orientation and femoral head asphericity, with little emphasis on the effect of version of the femoral neck. A biomechanical model was developed to determine the causative effect, if any, of femoral retroversion on hip contact stress and, if present, delineate the type of FAI with femoral neck retroversion. Five pairs of cadaveric hips (n = 10) were tested by loading the hip in 90° of flexion and measured the peak joint pressure and the location of the peak joint pressure. The experiment was repeated after performing a subtrochanteric osteotomy and retroverting the proximal femur by 10°. Ten hips were successfully tested, with one hip excluded due to an outlier value for peak joint pressure. Retroversion of the proximal femur significantly increased the magnitude of mean peak joint pressure. With retroversion, the location of the peak joint pressure was shifted posteroinferiorly in all cases. In conclusion, femoral neck retroversion increases peak joint pressure in the flexed position and may act as a cause of femoroacetabular impingement. The location of peak joint pressure suggests a pincer-type impingement with retroversion. The version of femoral neck should be assessed as a possible causative factor in patients with FAI, especially those with pincer-type impingement.

Revision TKA for Flexion Instability Improves Patient Reported Outcomes

Instability is a major cause of early revision of total knee arthroplasty (TKA), of which flexion instability is a major subset. We analyzed radiologically evident corrections, patient reported outcome and complications associated with revision TKA for flexion instability in a retrospective cohort of 37 patients with minimum one year follow up. Following revision surgery, there was a significant increase in mean posterior condylar offset ratio and a significant decrease in tibial slope while the level of joint line was not significantly altered. Patient reported version of knee society score showed significant improvement with surgery and 26 of 37 patient reported perceptible improvement on a 7-point Likert scale.

LEVEL OF EVIDENCE

Level IV, Case series. See the Guidelines for Authors for a complete description of levels of evidence.

Validity and reliability of radiographic knee osteoarthritis measures by arthroplasty surgeons

Most orthopedic surgeons do not routinely use radiographic classification systems to grade the extent of joint space narrowing in patients considered for total knee arthroplasty. The authors compared the validity and reliability of radiographic measures of tibiofemoral osteoarthritis by 2 experienced and 2 inexperienced orthopedic surgeons on individuals who subsequently underwent total knee arthroplasty. The Kellgren-Lawrence and the Osteoarthritis Research Society International classification systems were used by all surgeons to score the radiographs in 116 individuals in the Osteoarthritis Initiative, a federally funded cohort study of individuals with or at risk of knee osteoarthritis. Validity was judged based on comparison with the criterion centrally adjudicated consensus measures obtained by Osteoarthritis Initiative investigators. Weighted kappa, a chance corrected agreement index, was used to describe validity and reliability. Validity and intrarater reliability were substantial to almost perfect for 1 experienced and 1 inexperienced surgeon, with weighted kappas ranging from 0.76 to 0.96 for the surgical knees. The other experienced and inexperienced surgeons demonstrated moderate to substantial validity, with weighted kappas ranging from 0.43 to 0.70 and lower intrarater reliability. Interrater reliability was generally less than intrarater reliability. With minimal training, some surgeons can obtain valid and reliable measurements of knee osteoarthritis status in individuals who eventually undergo total knee arthroplasty. Measurement quality does not appear to be dependent on extent of surgeon experience. Some surgeons require additional training to become proficient in the radiographic classification systems, and future research should examine this issue.

Extent of tibiofemoral osteoarthritis before knee arthroplasty: multicenter data from the osteoarthritis initiative

BACKGROUND

Knee arthroplasty traditionally is recommended for persons with substantial disability and disabling pain attributable to moderate or severe osteoarthritis (OA). Pain and functional status after arthroplasty may be influenced by the extent of knee OA before surgery and recent evidence suggests persons with less severe knee OA before undergoing TKA have greater pain levels and worse function than persons with more severe knee OA.

QUESTIONS/PURPOSES

We determined the proportion of patients undergoing knee arthroplasty who had less than moderate knee OA before surgery and who had either a radiographically normal medial or lateral joint space before surgery.

METHODS

One hundred sixteen persons in the Osteoarthritis Initiative underwent knee arthroplasty during a 3-year period. Ninety-seven of the 116 patients (84%) had radiographs available less than 1 year before surgery and were included. We used Z-tests to determine whether the proportion of patients with a modified Kellgren-Lawrence (KL) grade of 3 or higher differed from literature-based estimates. In addition, we described the proportion of patients with medial and lateral joint space narrowing.

RESULTS

The proportion of patients with a modified KL grade of 3 or higher was 0.81 (95% CI, 0.73-0.89) and was less than the 0.95 estimated population proportion. Of the patients who underwent knee arthroplasty, 85% (82 of 97 knee arthroplasties) had at least one tibiofemoral joint compartment that had no joint space narrowing. One in six patients with OA who underwent knee arthroplasty had a KL grade of 2 or lower.

CONCLUSIONS

Variation in the extent of tibiofemoral OA in patients preparing for joint arthroplasty is greater than previously described. A greater percentage of patients undergoing knee arthroplasty may be at risk for increased pain and poorer function than previously assumed after surgery because of less severe knee OA before surgery.

LEVEL OF EVIDENCE

Level I, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

Role of the coronoid process in varus osteoarticular stability of the elbow

The role of the coronoid process in varus osteoarticular stability of the elbow was investigated in 10 cadaveric elbows. Testing was performed at multiple flexion angles after incremental removal of the coronoid. At each flexion angle, removal of more than 50% of the coronoid produced a statistically significant decrease in the load resisting varus displacement compared with all lesser resection levels (P < .003). There was a trend for decreasing load after removal of 50% of the coronoid. The mean decrease in load across all flexion angles was 10.1%, 50.4%, and 75.4% after removal of 50%, 75%, and 100% of the coronoid, respectively. Resistance to varus displacement tended to decrease more as a percent of control at lower flexion angles than at higher flexion angles after removal of more than 50% of the coronoid. The coronoid process was found to be a key varus stabilizer in the elbow and may contribute more to elbow stability in extension than in flexion.

Dental fluorosis and caries prevalence in children residing in communities with different levels of fluoride in the water

OBJECTIVES

This study investigated the prevalence of dental fluorosis and caries in 7-14-year-old children residing in communities with negligible (NF: 0.2 ppm), optimal (OPF: 1.0 ppm), and four-times optimal (4X OPF: 4.0 ppm) naturally occurring fluoride in their water systems.

METHODS

Examinations were performed on 344 children who were lifetime residents of their communities.

RESULTS

Whether using the tooth surface index of fluorosis or Dean's index, children examined in the 4X OPF community had the highest prevalence of dental fluorosis. While the severity of fluorosis seen in the OPF and NF communities was mild in appearance, the results indicate that fluorosis does occur in optimally and negligibly fluoridated communities. Compared to the NF community, DMFT and DMFS scores in the OPF community were 9.2 percent and 21.2 percent lower, respectively.

CONCLUSIONS

The ingestion of water containing 1 ppm or less fluoride during the time of tooth development may result in dental fluorosis, albeit in its milder forms. However, in these times of numerous products containing fluoride being available, children ingesting water containing 1 ppm fluoride continue to derive caries protection compared to children ingesting water with negligible amounts of fluoride. Thus, the potential for developing a relatively minor unesthetic condition must be weighed against the potential for reducing dental disease.

Dielectric compound parabolic concentrating solar collector with a frustrated total internal reflection absorber

Coupling a dielectric compound parabolic concentrator (DCPC) to an absorber across a vacuum gap by means of frustrated total internal reflection (FTIR) can theoretically approach the maximum concentration permitted by physical laws, thus allowing higher radiative fluxes in thermal applications. The calculated optical performance of 2-D DCPCs with FTIR absorbers indicates that the ratio of gap thickness to optical wavelength must be <0.22 before the optical performance of the DCPC is superior to that of the nondielectric CPC.

Proposed frustrated-total-reflection acoustic sensing method

Modulation of electromagnetic energy transmission through a frustrated-total-reflection device by pressure-induced changes in the index of refraction is proposed for use as an acoustic detector. Maximum sensitivity occurs for angles of incidence near the critical angle. The minimum detectable pressure in air is limited by Brownian noise. Acoustic propagation losses and diffraction of the optical beam by the acoustic signal limit the minimum acoustic wavelength to lengths of the order of the spatial extent of the optical beam. The response time of the method is fast enough to follow individual acoustic waves.