Search

Background: Metal debris and corrosion products generated from the taper junctions of modular joint replacements have been recognized as contributors to failure. Therefore, understanding the factors associated with increased taper wear and corrosion is fundamental to improving implant performance.Methods: A cohort of 85 large-diameter metal-on-metal heads and cups retrieved at revision surgery, after 10 to 96 months of service, was evaluated. First, metrology was conducted to quantify head taper material loss and implant articular surface wear. Then, joint frictional moments for each retrieved head-and-cup pair were measured during 10 cycles of simulated physiological gait in a biomechanical model. Taper material loss was evaluated for correlations with frictional moments, articular wear, head diameter, head-cup clearance, and time in vivo.Results: Peak resultant frictional moments ranged from 9.1 to 26.3 Nm, averaging 17.3 ± 2.7 Nm. Fretting and corrosion damage during in vivo service resulted in material loss from the head tapers ranging between 0.04 and 25.57 mm3, compared with combined head and cup articular wear of 0.80 to 351.75 mm3 in this cohort. Taper material loss was not correlated with higher frictional moments (R = -0.20 to 0.11, p = 0.07 to 0.81). Higher frictional moments from axial rotation were correlated with higher head and cup wear (R = 0.33, p < 0.01). The correlation between taper material loss and head diameter was weak and did not reach statistical significance (R = 0.20, p = 0.07). Taper material loss was not correlated with nominal head-cup clearance (R = 0.06, p = 0.6). Finally, taper material loss increased significantly over time (R = 0.34, p < 0.01).Conclusions: Despite serious concerns regarding trunnionosis, volumes of head taper wear were generally lower than those of articular surface wear. There was no statistical correlation between taper wear and frictional moments. Therefore, the results suggest that high friction in metal-on-metal implants does not contribute to higher material loss at the head taper, despite high bending moments.Clinical Relevance: The amount of metal debris and corrosion products from taper junctions of the joint arthroplasties, widely recognized as an insidious cause of failure, was not correlated with joint frictional moments. Multiple factors affect taper wear: implant design, material, size, surface finish, and patient weight and activity level. However, in the present cohort, high friction of metal-on-metal total hip replacements likely did not contribute to increased volume of material loss at taper interfaces, despite increased moments at the locations of taper material loss. [ABSTRACT FROM AUTHOR]

Background: Developed at the University of Iowa in 1950, the Ponseti method to manage idiopathic clubfoot deformity was slow to gain wide acceptance until the mid-1990s. There is a paucity of intermediate and long-term outcome studies involving this technique, with nearly all such studies coming from a single institution. The purpose of this study is to report the contemporary outcome of patients with clubfoot deformity whose feet were managed with the Ponseti method and who were followed to ≥5 years old, to provide outcome expectations for parents and for clinicians managing patients with idiopathic clubfoot.Methods: Families of infants seen in our clinic diagnosed with idiopathic clubfoot since July 2006 were prospectively invited to participate in our institutional review board-approved study. Patients who received no prior outside treatment and had a minimum follow-up to the age of 5 years were included. Demographic, treatment, and outcome data were collected. To provide an array of outcome measures, both the Dallas outcome criteria and the Roye disease-specific instrument (DSI) were used.Results: One hundred and one patients met the inclusion criteria. The mean length of follow-up (and standard deviation) was 81.1 ± 17.1 months. Initial correction was achieved in all feet. Thirty-seven percent of families reported that they were adherent with the bracing protocol; 68% of patients had ≥1 relapse, and 38% underwent a tendon transfer. With the Dallas criteria, 62% had outcomes rated as good, 38% had outcomes rated as fair, and no patient had an outcome rated as poor. With the Roye DSI, most families were generally very satisfied with the function and appearance of the feet.Conclusions: Satisfactory results at intermediate follow-up were achieved using the Ponseti method. However, despite a better understanding of the Ponseti method and the importance of longer post-corrective brace use, the need for anterior tibial tendon transfer remains an important adjunct to the Ponseti method. Brace adherence also continues to be a critical clinical issue.Level Of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence. [ABSTRACT FROM AUTHOR]

In the article, the author comments on the issue of oxidation in never-irradiated ultra-high molecular weight polyethylene (UHMWPE) components from revised hip, shoulder, knee, and ankle joint replacements. Other topics include the developments on the use of polyethylene material in joint replacement, and the effects of gamma irradiation on the sterilization of implants.

Background: A successful outcome for the treatment of idiopathic clubfoot is believed to require adequate adherence to brace use. Previous studies have relied on parental reporting of brace application. We used temperature sensors to determine the adherence to the bracing protocol, the accuracy of parent-reported use, and differences in adherence between patients who experienced relapse of deformity and those who did not.Methods: Using wireless sensors attached to brace sandals, we monitored brace wear over a 3-month period in this cross-sectional study involving 48 patients in 4 age-based groups: 6 to 12 months (Group 1), >1 to 2 years (Group 2), >2 to 3 years (Group 3), and >3 to 4 years (Group 4). Parents were blinded to the purpose of the sensors. The mean number of hours of daily brace use as measured by the sensors was compared with the physician-recommended hours and parent-reported hours of brace use.Results: Sensors were retrieved from 44 of 48 patients. Overall, the median brace use recorded by the sensors was 62% (range, 5% to 125%) of that recommended by the physician, and 77% (range, 6% to 213%) of that reported by the parents. For Groups 1 to 3, the difference between the physician-recommended and measured number of hours of daily brace use was significant (p ≤ 0.002), and the difference between the parent-reported and measured number of hours of daily brace use was also significant (p ≤ 0.013). Eight (18%) of the 44 patients who completed the study experienced relapse during the period of monitoring; most importantly, the mean number of hours of brace wear for these patients, 5 hours per day (median, 4; and standard deviation [SD], 3 hours per day) was significantly lower than the 8 hours per day for those who did not experience relapse (median, 9; and SD, 5 hours per day) (p = 0.045).Conclusions: The present study objectively quantified the number of daily hours of post-corrective brace wear for patients with clubfoot in varying age groups and provides an estimate of the number of hours required to avoid relapse.Level Of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence. [ABSTRACT FROM AUTHOR]

Unlabelled: Liner cementation into a preexisting stable socket may reduce the morbidity of revision hip arthroplasty and preserve acetabular bone. However, the long-term outcomes of this technique remain unknown. The purpose of this report was to analyze the long-term results of a previously reported cohort of patients. Cementation of thirty-two liners (seventeen polyethylene and fifteen metal liners) into preexisting sockets was performed during revision hip arthroplasty, and the patients were followed for a minimum of two years. A retrospective chart review was performed to investigate the complications and survivorship. The mean duration of follow-up was 12.7 years (range, 2.1 to 19.1 years), with ten hips requiring rerevision at a mean of 6.4 years (range, 1.0 to 15.5 years). Nine patients experienced posterior dislocations, and two hips required rerevision for instability. Liner dissociation from the shell occurred in two patients. Survivorship analysis, with rerevision as the end point, demonstrated ten and fifteen-year survivorship of 77.3% and 68.8%, respectively. Dissociation of the cemented liner from the acetabular shell was an infrequent cause of failure despite long-term follow-up. Given the high rate of dislocations in this study, careful patient selection and surgical technique should be considered.Level Of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence. [ABSTRACT FROM AUTHOR]

Liner cementation into a preexisting stable socket may reduce the morbidity of revision hip arthroplasty and preserve acetabular bone. However, the long-term outcomes of this technique remain unknown. The purpose of this report was to analyze the long-term results of a previously reported cohort of patients. Cementation of thirty-two liners (seventeen polyethylene and fifteen metal liners) into preexisting sockets was performed during revision hip arthroplasty, and the patients were followed for a minimum of two years. A retrospective chart review was performed to investigate the complications and survivorship. The mean duration of follow-up was 12.7 years (range, 2.1 to 19.1 years), with ten hips requiring rerevision at a mean of 6.4 years (range, 1.0 to 15.5 years). Nine patients experienced posterior dislocations, and two hips required rerevision for instability. Liner dissociation from the shell occurred in two patients. Survivorship analysis, with rerevision as the end point, demonstrated ten and fifteen-year survivorship of 77.3% and 68.8%, respectively. Dissociation of the cemented liner from the acetabular shell was an infrequent cause of failure despite long-term follow-up. Given the high rate of dislocations in this study, careful patient selection and surgical technique should be considered. [ABSTRACT FROM AUTHOR]

Background: The Ponseti method is an established approach to treating idiopathic clubfoot in infants. The method involves a period of cast immobilization and postcorrective bracing that potentially interferes with normal movements of the lower extremities. In the present study, we investigated the age at which infants who had idiopathic clubfoot treated using the Ponseti method achieved independent walking. Methods: We prospectively evaluated patients of a single surgeon. Included in the study were all patients with idiopathic clubfoot who were full term at birth, were no more than twelve weeks of age at the start of treatment, had received no prior outside treatment, and were followed for a minimum of twenty-four months. Results: Ninety-four patients were included. The mean age at which patients began walking independently was 14.5 ± 2.6 months (range, ten to twenty-two months). By eighteen months, 90% of the patients were walking without assistance. Patients with moderate or severe clubfoot deformity began walking earlier than did patients with very severe deformity (a mean of 14.2 months compared with 15.8 months; p = 0.03). Patients who experienced a relapse before learning to walk began walking later than those who did not relapse (a mean of 15.9 months compared with 14.2 months; p = 0.04). Other patient and treatment-related variables had no significant influence on the onset of walking. Conclusions: On the basis of our findings, parents of infants with idiopathic clubfoot treated using the Ponseti method may expect their child to achieve independent walking approximately two months later than infants without clubfoot deformity. A greater delay may be expected for those patients who have a very severe deformity or those who experience a deformity relapse. [ABSTRACT FROM AUTHOR]

Background: Many orthopaedic surgeons treat tibial shaft fractures in children with a period of non-weight-bearing after application of a long leg cast, presumably to prevent fracture angulation and shortening. We hypothesized that allowing children to immediately bear weight as tolerated in a cast with the knee in 10° of flexion would lessen disability, without increasing the risk of unacceptable shortening or angulation. Methods: We divided eighty-one children, between the ages of four and fourteen years, with a low-energy, closed tibial shaft fracture into two groups. One group (forty children) received a long leg cast with the knee flexed 60° and were asked not to bear weight. The second group (forty-one children) received a long leg cast with the knee flexed 10° and were encouraged to bear weight as tolerated. All patients were switched to short leg walking casts at four weeks. We compared time to healing, overall alignment, shortening, and physical disability as determined by the Activities Scale for Kids-Performance (ASK-P) questionnaire. Results: The mean time to fracture union was 10.8 weeks in both groups (p = 0.47). At the time of healing, mean coronal alignment was within 1.3° in both groups, mean sagittal alignment was within 1°, and mean shortening was <0.5 mm, with no significant differences. The ASK-P scores showed that both groups had overall improvement in physical functioning over time. However, at six weeks, the children who were allowed to bear weight as tolerated had better overall scores (p = 0.03) and better standing skills (p = 0.01) than those who were initially instructed to be non-weight-bearing. Conclusions: Children with low-energy tibial shaft fractures can be successfully managed by immobilizing the knee in 10° of flexion and encouraging early weight-bearing, without affecting the time to union or increasing the risk of angulation and shortening at the fracture site. [ABSTRACT FROM AUTHOR]

Background: In the late 1990s, renewed interest emerged in less invasive treatment options, most notably the Ponseti method, to correct idiopathic clubfoot deformity. Recently, reports from several centers have demonstrated that such minimally invasive techniques may be used reliably to correct this complex deformity. The present study sought to determine whether the rate of extensive surgical releases to treat idiopathic clubfoot in the United States has decreased. Methods: We used data from the Centers for Disease Control and Prevention and the Nationwide Inpatient Sample to determine the number of live births, the number of patients diagnosed with clubfoot, and the number of extensive surgical releases that were performed each year from 1996 to 2006. The trends over time were evaluated with use of regression analysis, and changes in frequency were analyzed with use of time series analysis. The percentage of clubfeet that were treated with surgery in each year was calculated by dividing the number of surgical release procedures by the number of clubfoot diagnoses. Results: Between 1996 and 2006, the estimated number of patients under six months of age diagnosed with clubfoot remained fairly constant, averaging 2140 infants per year. The linear equation estimated a slight decrease of approximately thirty-one infants with clubfoot per year (R2 = 0.51, p < 0.05). In contrast, in the same decade, the estimated number of surgical releases performed in patients less than twelve months of age decreased substantially, from 1641 releases in 1996 to 230 releases in 2006. The linear equation estimated a decrease of approximately 157 surgical releases per year (R2 = 0.83, p < 0.05). The trend analysis indicated that the percentage of clubfeet treated with surgical release generally decreased over time at a rate of 6.7% per year, decreasing from just over 70% in 1996 to just over 10% in 2006 (R2 = 0.81, p < 0.05). Conclusions: In the United States between 1996 and 2006, the rate of extensive surgery to treat idiopathic clubfoot in patients less than twelve months old decreased substantially. This trend is likely due to an increased use of less invasive techniques, such as the Ponseti method, which a growing body of evidence has shown to be a viable treatment option for clubfoot. [ABSTRACT FROM AUTHOR]

Background: Functional and health-related quality-of-life data on a population of patients with hallux valgus are lacking. Similarly, the correlation of the severity of the deformity with these measures is unknown. Methods: Two hundred and eighty-five women with an average age of forty-nine years who were scheduled for bunion surgery were enrolled in the study. The patients completed a baseline American Academy of Orthopaedic Surgeons (AAOS) foot and ankle outcomes questionnaire, which includes the Short Form-36 (SF-36) and a specific lower-extremity section on the foot and ankle. Preoperative radiographic data with regard to the hallux valgus angle and the intermetatarsal angle were stratified into groups according to the severity of the deformity (mild, moderate, or severe). The data were then stratified into age-groups consistent with those reported for the SF-36, and the results were compared with the SF-36 scores for the general population. The global foot and ankle score and the shoe comfort score were compared with general population scores that were published previously. The severity of the preoperative deformity was correlated with the baseline scores. Results: General health scores were noted to be relatively stable throughout the age-groups for patients with bunions, with the older groups demonstrating better scores than the general population. Bodily pain scores were consistently worse for patients with a bunion through all age-groups compared with the general population. The average global foot and ankle score and the shoe comfort score were significantly lower (p < 0.001 for both) for the patients with a bunion than for the general population. The severity of the preoperative deformity did not correlate with any of the outcome scores. Conclusions: The bodily pain score from the SF-36 appears to be a sensitive measure of problems experienced by patients undergoing bunion surgery. Surprisingly, the severity of the deformity as measured radiographically did not correlate with any of the fifteen scores measured. These data may serve as a baseline for clinical hallux valgus studies with use of the SF-36 or the AAOS outcomes questionnaire. [ABSTRACT FROM AUTHOR]

Background: Although the orientation of the femoral component has been shown to influence the outcome of total hip replacement, its effect on the clinical outcome of surface arthroplasty has not been studied, to our knowledge. The purpose of this study was to examine the relationship between femoral component positioning and the outcome of a surface arthroplasty of the hip. Methods: We reviewed the results of ninety-four hybrid metal-on-metal surface arthroplasties in patients who were forty years old or younger at the time of the operation and were followed for a minimum of two years or until the prosthesis failed. Measurements of the hip reconstruction were made on the anteroposterior pelvic radiograph. The correlation between the orientation of the femoral component and the outcome of the arthroplasty was evaluated, as were stresses within the resurfaced femoral head as a function of the orientation of the femoral component. Results: The mean duration of follow-up was 4.2 years. Thirteen hips had an adverse outcome, defined as conversion to a total hip replacement, radiolucency of >1 mm in thickness adjacent to the femoral stem, or narrowing of the femoral neck of >10%. The mean femoral stem-shaft angle in the coronal plane was 138°, with the hips that had an adverse outcome having a significantly lower mean angle than the rest of the cohort (133° compared with 139°, p 0.03). Hips with an angle of ≤130° had an increase in the relative risk of an adverse outcome by a factor of 6.1 (p < 0.004). In the entire cohort, stresses in the superior aspect of the resurfaced femoral head were substantially lower during slow walking than they were during fast walking (7.1 N/mm² compared with 14.2 N/mm²). Conclusions: Optimizing the femoral stem-shaft angle toward a valgus orientation during the preparation of the femoral head is important when a hip is being reconstructed with a surface arthroplasty because the resurfaced hip transmits the load through a narrow critical zone in the femoral head-neck region and the valgus angulation may reduce these stresses. Level of Evidence: Therapeutic study, Level III-2 (retrospective cohort study). See Instructions to Authors for a complete description of levels of evidence. [ABSTRACT FROM AUTHOR]

Background: During revision hip replacement surgery, the cementless acetabular shell is often well fixed but the locking mechanism may be ineffective. Cementing a new liner into the existing acetabular shell (the double-socket technique) can provide a simple solution. The purposes of the present study were to review our initial clinical results and to define the potential limitations of this technique.Methods: Thirty-two hips with a preexisting well-fixed acetabular socket that had been in situ for an average of 8.6 years were treated with the insertion of a new polyethylene liner (seventeen hips) or a metal liner (fifteen hips) with use of cement. The indication for this technique was a deficient locking mechanism in twenty-two hips and the unavailability of a matching liner in ten hips. Anteroposterior radiographs of all hips were analyzed by a single independent reviewer.Results: The mean duration of follow-up was 5.1 years. Six hips required a reoperation after a mean of 29.7 months; the reasons for the reoperations included aseptic failure of the acetabular construct (four hips), instability (one hip), and sepsis (one hip). The University of California at Los Angeles hip scores improved significantly (p < 0.001) compared with the preoperative values; specifically, the mean score improved from 6.2 to 9.1 for pain, from 6.3 to 8.3 for walking, from 6.2 to 7.8 for function, and from 4.7 to 5.8 for activity. The prevalence of dislocation was 22%. Kaplan-Meier analysis with revision as the end point revealed a five-year survival rate of 78% (95% confidence interval, 55% to 91%).Conclusions: The double-socket technique is a good alternative to acetabular socket removal for suitable candidates who have a well-fixed cementless socket with an inner diameter that is larger than the outer diameter of the cemented liner. This technique preserves acetabular bone stock and permits conversion to alternate bearing surfaces. We believe, however, that removal of a well-fixed acetabular shell or the use of a constrained liner should be strongly considered for patients with a history of hip instability. [ABSTRACT FROM AUTHOR]

Background: Although current designs of cemented femoral stems for total hip replacement include both those with and those without a flanged shape at the proximal end, the influence of anteroposterior dorsal flanges on the fixation of the stem is not completely understood. The purpose of this study was to assess the effects of flanges on femoral stem stability and load transfer to the femur with use of an in vitro model. Methods: We measured femoral surface strains and three-dimensional micromotion in synthetic femora under cyclic loading with four types of stems: those with flanges and those without flanges in two sizes each. The four types of stems were otherwise identical; that is, all of them were straight, polished, and collarless. Stem-cement micromotion measurements and strain measurements were repeated with three stems of each type, whereas bone-cement micro- motion measurements were made with one stem of each type. Results: Flanges had a greater influence on femoral strains and micromotion than did the difference in the cement thickness resulting from the different stem sizes. Specifically, the flanged stems produced greater strains on the me- dial femoral surface but smaller strains on the anterior surface than did the non-flanged stems. Flanged stems achieved tighter mechanical interlock within the cement, but these stems increased bone-cement micromotion. Specifically, the motion per cycle of flanged stems within the cement mantle was smaller than that of non-flanged stems, whereas the motion per cycle of the cement mantle within the femoral canal was greater with the flanged stems than with the non-flanged stems. Conclusions: Flanges on a total hip femoral stem increase the interlock between the stem and the cement and decrease the proximal-medial stress-shielding. However, these advantages occur with increased bone-cement interface motion, which may be detrimental to the survival of the implant. [ABSTRACT FROM AUTHOR]

Background: The optimum surface roughness of cemented femoral stems used for total hip replacement is a subject of controversy. While rougher surfaces provide stronger cement adhesion, it has been hypothesized that polished, tapered, noncollared stems settle into the cement mantle, providing improved stability. However, the effects of surface finish on the stability of straight, cemented stems tapered only in the coronal plane are not known.Methods: Using composite model femora, we assessed the initial stability of a straight, cemented femoral stem as a function of surface roughness, the presence or absence of a collar, stem size, and the resultant cement thickness under simulated walking and stair-climbing loads. Otherwise identical stems were manufactured with polished or rough surfaces, with or without a collar, in two different sizes. We isolated these three variables and compared their relative contributions to the motion at the stem-cement interface throughout cyclic loading. We defined three indicators of stability: per-cycle motion, rate of migration, and final migration.Results: Surface roughness had a greater influence on per-cycle motions than did the presence or absence of a collar or cement thickness. Specifically, in the medial-lateral direction, per-cycle motion of polished stems was 43 micro m greater than that of rough stems (p < 0.01). None of the per-cycle motions decreased over the 77,000 load cycles. In contrast, with all stems, the rate of migration decreased over the course of cyclic loading, but the rate of migration of the polished stems was greater than that of the rough stems. Final migrations of the stems over the course of loading were generally distal, medial, and into retroversion. Compared with rough stems, polished stems had 8 to 18 micro m more axial migration (p < 0.001), 48 micro m more anterior-posterior migration (p < 0.001), and 0.4 degrees more rotational migration (p = 0.01).Conclusions: andClinical Relevance: The results indicated that, for cemented, straight femoral stems tapered only in the coronal plane, a rough surface offers the advantage of less per-cycle motion. These results may apply to widely used cemented stem designs based on the profile of the original Charnley femoral component, which has approximately parallel anterior and posterior aspects. [ABSTRACT FROM AUTHOR]

Although a number of methods are used to estimate polyethylene liner wear from radiographs of total hip replacements, there is no consensus with regard to the accuracy of these methods. The purpose of this study was to compare the accuracy of several such measurement methods with use of both laboratory radiographs and routine clinical radiographs. A phantom apparatus was designed to simulate random values of three-dimensional wear, with varying degrees of cup abduction and anteversion, and to obtain anteroposterior and cross-table lateral radiographs with each value. Wear was measured with use of the Charnley duoradiographic method, the Livermore method, and the method described by Dorr and Wan, as well as with use of PolyWare and Hip32 software packages, both with and without three-dimensional measurements. Clinical wear was measured from conventional radiographs made prior to revision surgery in fourteen patients and was compared with wear measured directly from the retrieved liners with use of a coordinate measuring machine. With laboratory radiographs, computerized methods of polyethylene wear measurement offered distinctly greater accuracy than did manual methods; however, with clinical radiographs, they offered only slightly better accuracy. Although the increased accuracy of computerized methods may be necessary in research settings, manual methods provided sufficient accuracy for routine clinical assessment of wear. [ABSTRACT FROM AUTHOR]

The article presents the author's comments on the article Blood Metal Ion Thresholds to Identify Patients with Metal-on- Metal Hip Implants at Risk of Adverse Reactions to Metal Debris. An ExternalMulticenter Validation Study of Birmingham Hip Resurfacing and Corail- Pinnacle Implants, published in this issue. She opines on the failure of authors to link the observed ARMD risk factors.

The authors discuss a report within the issue, ‘‘Comparison of Ten-Year Survivorship of Hip Prostheses with Use of Conventional Polyethylene, Metal-on-Metal, or Ceramic-on-Ceramic Bearings," by Ingrid Milošev and colleagues. The study looked at complications such as aseptic loosening, component fracture, and osteolysis requiring reoperation. It is argued that the study should have also considered impingement of acetabular components, adverse tissue reaction, and the preferences of surgeons.

An introduction is presented in which the editor discusses various reports within the issue on topics including bisphosphonates, rehabilitation after anterior cruciate ligament reconstruction and hip arthroplasty.