Total Knee Arthroplasty Versus Education and Exercise for Knee Osteoarthritis: A Propensity-Matched Analysis

OBJECTIVE

We estimate the treatment effect of total knee arthroplasty (TKA) versus an education and exercise (Edu+Ex) program on pain, function, and quality of life outcomes 3 and 12 months after treatment initiation for knee osteoarthritis (OA).

METHODS

Patients with knee OA who had undergone TKA were matched on a 1:1 ratio with participants in an Edu+Ex program based on a propensity score fitted to a range of pretreatment covariates. After matching, between-group differences in improvement (the treatment effect) in Knee Injury and Osteoarthritis Outcome Score 12-item version (0, worst to 100, best) pain, function, and quality of life from baseline to 3 and 12 months were estimated using linear mixed models, adjusting for unbalanced covariates, if any, after matching.

RESULTS

The matched sample consisted of 522 patients (Edu+Ex, n = 261; TKA, n = 261) who were balanced on all pretreatment characteristics. At 12-month follow-up, TKA resulted in significantly greater improvements in pain (mean difference [MD] 22.8; 95% confidence interval [95% CI] 19.7-25.8), function (MD 21.2; 95% CI 17.7-24.4), and quality of life (MD 18.3; 15.0-21.6). Even so, at least one-third of patients receiving Edu+Ex had a clinically meaningful improvement in outcomes at 12 months compared with 75% of patients with TKA.

CONCLUSION

TKA is associated with greater improvements in pain, function, and quality of life, but these findings also suggest that Edu+Ex may be a viable alternative to TKA in a meaningful proportion of patients, which may reduce overall TKA need. Confirmatory trials are needed.

Total Hip Arthroplasty Versus Education and Exercise: A Propensity-Matched Analysis of 266 Patients Who Have Hip Osteoarthritis

BACKGROUND

Total hip arthroplasty (THA) for osteoarthritis (OA) is a major health system cost. Education and exercise (Edu+Ex) programs may reduce the number of THAs needed, but supporting data is limited. This study aimed to estimate the treatment effect of THA versus Edu+Ex on pain, function, and quality of life outcomes 3- and 12-months after treatment initiation for hip OA.

METHODS

Patients who had hip OA who underwent THA or an Edu+Ex program were included in this propensity-matched study. In 778 patients (Edu+Ex n = 303; THA n = 475), propensity scores were based on pre-treatment characteristics, and patients were matched on a 1:1 ratio. Between-group treatment effects (pain, function, and quality of life) were estimated as the mean difference in change from pre-treatment to 3- and 12-month follow-up using linear mixed models.

RESULTS

The matched sample consisted of 266 patients (Edu+Ex n = 133; THA n = 133) that were balanced on all pre-treatment characteristics except opioid use. At 12-month follow-up, THA resulted in significantly greater improvements in pain (mean difference [MD] 35.4; 95% CI [confidence interval] 31.4 to 39.4), function (MD 30.5; 95% CI 26.3 to 34.7), and quality of life (MD 33.6; 95% CI 28.8 to 38.4). Between 17 and 30% of patients receiving Edu+Ex experienced a surgical threshold for clinically meaningful improvement in outcomes, compared to 84 and 90% of THA patients.

CONCLUSIONS

A THA provides greater improvements in pain, function, and quality of life. A significant proportion of Edu+Ex patients had clinically meaningful improvements, suggesting Edu+Ex may result in THA deferral in some patients, but confirmatory trials are needed.

Hospital spending and length of stay attributable to perioperative adverse events for inpatient hip, knee, and spine surgery: a retrospective cohort study

BACKGROUND

The incremental hospital cost and length of stay (LOS) associated with adverse events (AEs) has not been well characterized for planned and unplanned inpatient spine, hip, and knee surgeries.

METHODS

Retrospective cohort study of hip, knee, and spine surgeries at an academic hospital in 2011-2012. Adverse events were prospectively collected for 3,063 inpatient cases using the Orthopaedic Surgical AdVerse Event Severity (OrthoSAVES) reporting tool. Case costs were retrospectively obtained and inflated to equivalent 2021 CAD values. Propensity score methodology was used to assess the cost and LOS attributable to AEs, controlling for a variety of patient and procedure factors.

RESULTS

The sample was 55% female and average age was 64; 79% of admissions were planned. 30% of cases had one or more AEs (82% had low-severity AEs at worst). The incremental cost and LOS attributable to AEs were $8,500 (95% confidence interval [CI]: 5100-11,800) and 4.7 days (95% CI: 3.4-5.9) per admission. This corresponded to a cumulative $7.8 M (14% of total cohort cost) and 4,290 bed-days (19% of cohort bed-days) attributable to AEs. Incremental estimates varied substantially by (1) admission type (planned: $4,700/2.4 days; unplanned: $20,700/11.5 days), (2) AE severity (low: $4,000/3.1 days; high: $29,500/11.9 days), and (3) anatomical region (spine: $19,800/9 days; hip: $4,900/3.8 days; knee: $1,900/1.5 days). Despite only 21% of admissions being unplanned, adverse events in these admissions cumulatively accounted for 59% of costs and 62% of bed-days attributable to AEs.

CONCLUSIONS

This study comprehensively demonstrates the considerable cost and LOS attributable to AEs in orthopaedic and spine admissions. In particular, the incremental cost and LOS attributable to AEs per admission were almost five times as high among unplanned admissions compared to planned admissions. Mitigation strategies focused on unplanned surgeries may result in significant quality improvement and cost savings in the healthcare system.

Yap regulates skeletal muscle fatty acid oxidation and adiposity in metabolic disease

Obesity is a major risk factor underlying the development of metabolic disease and a growing public health concern globally. Strategies to promote skeletal muscle metabolism can be effective to limit the progression of metabolic disease. Here, we demonstrate that the levels of the Hippo pathway transcriptional co-activator YAP are decreased in muscle biopsies from obese, insulin-resistant humans and mice. Targeted disruption of Yap in adult skeletal muscle resulted in incomplete oxidation of fatty acids and lipotoxicity. Integrated 'omics analysis from isolated adult muscle nuclei revealed that Yap regulates a transcriptional profile associated with metabolic substrate utilisation. In line with these findings, increasing Yap abundance in the striated muscle of obese (db/db) mice enhanced energy expenditure and attenuated adiposity. Our results demonstrate a vital role for Yap as a mediator of skeletal muscle metabolism. Strategies to enhance Yap activity in skeletal muscle warrant consideration as part of comprehensive approaches to treat metabolic disease.

Postoperative improvement in health-related quality of life: a national comparison of surgical treatment for focal (one- to two-level) lumbar spinal stenosis compared with total joint arthroplasty for osteoarthritis

BACKGROUND CONTEXT

The results of single-center studies have shown that surgical intervention for lumbar spinal stenosis yielded comparable health-related quality of life (HRQoL) improvement to total joint arthroplasty (TJA). Whether these results are generalizable to routine clinical practice in Canada is unknown.

PURPOSE

The primary purpose of this equivalence study was to compare the relative improvement in physical HRQoL after surgery for focal lumbar spinal stenosis (FLSS) compared with TJA for hip and knee osteoarthritis (OA) across six Canadian centers.

STUDY DESIGN/SETTING

A Canadian multicenter ambispective cohort study.

PATIENT SAMPLE

A cohort of 371 primary one- to two-level spinal decompression (n=214 with instrumented fusion) for FLSS (n=179 with degenerative lumbar spondylolisthesis [DLS]) was compared with a cohort of primary total hip (n=156) and knee (n=208) arthroplasty for OA.

OUTCOME MEASURES

The primary outcome was the change in preoperative to 2-year postoperative 36-Item Short Form Health Survey Physical Component Summary (PCS) score as reflected by the number of patients reaching minimal clinically important difference (MCID) and substantial clinical benefit (SCB).

METHODS

Univariate analyses were conducted to identify baseline differences and factors that were significantly related to outcomes at 2 years. Multivariable regression modeling was used as our primary analysis to compare outcomes between groups.

RESULTS

The mean age (years) and percent females for the spine, hip, and knee groups were 63.3/58.5, 66.0/46.9, and 65.8/64.3, respectively. All three groups experienced significant improvement of baseline PCS (p<.001). Multivariate analyses, adjusting for baseline differences (age, gender, baseline Mental Component Summary score, baseline PCS), demonstrated no significant differences in PCS outcome between spinal surgery and arthroplasty (combined hip and knee cohorts) patients with an odds ratio of 0.80 (95% confidence interval [CI], 0.57-1.11; p=.17) and 0.79 (95% CI, 0.58-1.09; p=.15) for achieving MCID or SCB, respectively. In subgroup analysis, spine and knee outcomes were not significantly different, with hip arthroplasty superior to both (p<.0001).

CONCLUSIONS

Significant improvement in physical HRQoL after surgical treatment of FLSS (including DLS) is consistently achieved nationally. Our overall results demonstrate that a comparable number of patients can expect to achieve MCID and SCB 2 years after surgical intervention for FLSS and total knee arthroplasty.

Complications after minimally invasive total knee arthroplasty as compared with traditional incision techniques: a meta-analysis

The primary objective of our meta-analysis was to compare the incidence of complications between minimally invasive surgery and standard total knee arthroplasty (TKA) approaches. We reviewed randomized controlled trials comparing minimally invasive TKA to standard TKA. After testing for publication bias and heterogeneity, the data were aggregated by random effects modeling. Our primary outcome was the number of complications. Our secondary outcomes were alignment outliers, Knee Society Function scores, and Knee Society Knee scores. The combined odds ratios for complications for the minimally invasive surgery group and alignment outliers were 1.58 (95% confidence interval, 1.01-2.47; P < .05) and 0.79 (95% confidence interval, 0.34-1.82; P = .58), respectively. The standard difference in means for Knee Society scores was no different between groups. Minimally invasive knee surgery should be approached with caution.

Relationship between body habitus and joint leptin levels in a knee osteoarthritis population

Synovial fluid (SF) leptin has been shown to have an association with cartilage degeneration. Our objective was to examine the relationship between different measures of body habitus and SF leptin levels in an end-stage knee osteoarthritis (OA) population. Sixty consecutive patients with knee OA were surveyed prior to surgery for demographic data. Body habitus was assessed with the body mass index (BMI), waist circumference (WC), and waist-hip ratio (WHR). SF and serum samples were analyzed for leptin and adiponectin using specific ELISA. Nonparametric correlations and linear regression modeling was used to identify the relationship between the measures of body habitus and SF leptin levels. Females had greater levels of leptin than males in both the serum and SF. Significant correlations were found between SF leptin levels and BMI and WC (R(2) 0.44 and 0.38, respectively; p < 0.05). Regression modeling showed that female gender and WC were independent predictors of a greater SF leptin level independent of age, BMI, and presence of diabetes (p < 0.05). WC may be a more accurate measure of body habitus than BMI in the relationship between the metabolic effects of adipose tissue and OA.

Effect of sex and living arrangement on the timing and outcome of joint replacement surgery

BACKGROUND

Studies have shown that women present for surgery at an older age and with greater dysfunction than do men; however, the explanation for this finding is unclear. We investigated the impact living status (alone or with another person) and sex on the timing and outcomes of hip and knee replacement surgery.

METHODS

We surveyed 1722 patients undergoing primary hip or knee replacement surgery. Relevant covariates including demographic data, body mass index, sex, living status and comorbidities were recorded. We assessed joint pain and functional status before surgery and at 3 months and 1 year after surgery using the Western Ontario McMaster University Osteoarthritis Index (WOMAC) scores for pain and function.

RESULTS

In total, 22.9% (395) of all patients (29.3% of women and 14.1% of men) were living alone at the time of surgery. Compared with patients who lived with another person, those who lived alone were significantly older, had greater comorbidity and reported greater joint pain and dysfunction before surgery and 3 months and 1 year after surgery. Living alone and female sex independently predicted a greater preoperative WOMAC score, and living alone predicted an older age at the time of surgery and a poorer 1-year outcome.

CONCLUSION

Patients who live alone may delay joint replacement surgery until an older age and have greater joint pain and dysfunction than those who live with another person, leading to poorer 1-year outcomes.

Inpatient compared with home-based rehabilitation following primary unilateral total hip or knee replacement: a randomized controlled trial

BACKGROUND

Home-based rehabilitation is increasingly utilized to reduce health-care costs; however, with a shorter hospital stay, the possibility arises for an increase in adverse clinical outcomes. We evaluated the effectiveness and cost of care of home-based compared with inpatient rehabilitation following primary total hip or knee joint replacement.

METHODS

We randomized 234 patients, using block randomization techniques, to either home-based or inpatient rehabilitation following total joint replacement. All patients followed standardized care pathways and were evaluated, with use of validated outcome measures (Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC], Short Form-36, and patient satisfaction), prior to surgery and at three and twelve months following surgery. The primary outcome was the WOMAC function score at three months after surgery.

RESULTS

The mean length of stay (and standard deviation) in the acute care hospital was 6.3 +/- 2.5 days for the group designated for inpatient rehabilitation prior to transfer to that facility compared with 7.0 +/- 3.0 days for the home-based rehabilitation group prior to discharge home (p = 0.06). The mean length of stay in inpatient rehabilitation was 17.7 +/- 8.6 days. The mean number of postoperative home-based rehabilitation visits was eight. The prevalence of postoperative complications up to twelve months postoperatively was similar in both groups, which each had a 2% rate of dislocation and a 3% rate of clinically important deep venous thrombosis. The prevalence of infection was 0% in the home-based group and 2% in the inpatient group. None of these differences was clinically important. Both groups showed substantial improvements at three and twelve months, with no significant differences between the groups with respect to WOMAC, Short Form-36, or patient satisfaction scores (p > 0.05). The total episode-of-care costs (in Canadian dollars) for the inpatient rehabilitation and home-based rehabilitation arms were $14,532 and $11,082, respectively (p < 0.01).

CONCLUSIONS

Despite concerns about early hospital discharge, there was no difference in pain, functional outcomes, or patient satisfaction between the group that received home-based rehabilitation and the group that had inpatient rehabilitation. On the basis of our findings, we recommend the use of a home-based rehabilitation protocol following elective primary total hip or knee replacement as it is the more cost-effective strategy.

Comparison of early and delayed fixation of subcapital hip fractures in patients sixty years of age or less

BACKGROUND

Subcapital hip fractures in younger patients are generally treated with internal fixation rather than with primary hemiarthroplasty, which is generally reserved for older, low-demand patients. Avascular necrosis can occur following this injury because of disruption of the femoral head blood supply. Some believe that emergent fracture reduction is necessary to minimize the risk of avascular necrosis. The purposes of this study were (1) to investigate the functional outcomes of subcapital hip fractures in patients sixty years old or younger and (2) to compare the rates of avascular necrosis after early and delayed fracture fixation.

METHODS

This retrospective study included adults in whom a subcapital hip fracture had been treated with reduction and internal fixation when they were sixty years of age or less and who had been followed clinically for a minimum of two years. The patients were divided into two groups: those treated with early fixation (within twelve hours after the injury) and those treated with delayed fixation (more than twelve hours after the injury). Functional outcomes were assessed with use of the Short Form-36 and the Western Ontario and McMaster University (WOMAC) Osteoarthritis Index. The rates of avascular necrosis were compared between the two groups.

RESULTS

Thirty-eight patients (average age, 46.4 years) participated in the study. Twenty-nine patients had a displaced subcapital hip fracture. Fifteen patients underwent early fracture fixation, and the remainder underwent delayed fixation. No differences in the Short Form-36 (p = 0.68) or WOMAC (p = 0.69) scores were seen between the early and delayed fixation groups. Radiographic evidence of avascular necrosis developed in six patients treated with delayed fixation, one of whom had had an undisplaced fracture preoperatively, and in no patient treated with early fixation. The difference in the rates of avascular necrosis was significant (p = 0.03).

CONCLUSIONS

Although delayed surgical treatment of subcapital hip fractures was associated with a higher rate of avascular necrosis, this complication did not significantly affect functional outcome. Longer follow-up is required to assess the effect of avascular necrosis on the development of arthritis and on long-term patient function. Although the results could be biased because patients were not randomly assigned to delayed or early fixation, the data suggest that urgent reduction and fracture fixation within twelve hours after a displaced subcapital hip fracture in high-demand patients may be associated with a reduced rate of radiographic signs of avascular necrosis.

Patient factors affecting autologous and allogeneic blood transfusion rates in total hip arthroplasty

Factors that place patients undergoing total hip arthroplasty (THA) at increased risk of receiving an allogeneic or autologous blood transfusion may aid in determining which patients should predonate blood. The records of 354 consecutive patients undergoing THA were retrospectively reviewed to determine patient factors related to transfusion requirement. The risk of transfusion requirement was most strongly correlated with low preoperative hemoglobin level, but also with older age, higher American Society of Anesthesiologists physical status rating, female sex, cemented arthroplasty, and revision surgery. These patients were also least likely to predonate blood, likely because of their comorbid status.

The effect of a tibial baseplate undersurface peripheral lip on cement penetration in total knee arthroplasty

Many total knee arthroplasty (TKA) tibial baseplates have a peripheral lip or cement pocket theoretically to increase cement penetration by decreasing edge escape of the cement squeeze film on baseplate impaction. We reviewed 177 consecutive TKAs (89 nonlipped and 87 lipped baseplates) performed by a single surgeon, using the same third-generation tibial cementation techniques. Cement penetration patterns of the lateral 12 mm of proximal tibia were examined by a semiautomatic computerized digital image analysis technique. Penetration in the lipped baseplate was double that of the nonlipped baseplate at the component's lateral edge (P<.05) and continued to be statistically significantly greater to 4 mm from edge. From 5 to 7 mm, the difference was no longer statistically significant, and from 8 to 12 mm, the penetration was equal.

The effect of freezing and intraosseous fluid on the stiffness behavior of canine trabecular bone

The effect of disrupting the intraosseous fluid compartment and freezing on the mechanical stiffness of trabecular bone in intact canine femoral head specimens was investigated. Twenty-four skeletally mature dogs were divided into two groups. Twelve paired fresh femora were tested and 12 paired femora were tested after freezing at -20 degrees C. The intact femoral head specimens were subjected to a load of physiologic magnitude, and then the stiffness of the underlying trabecular bone was determined in intact femora, in drilled femora with a disrupted intraosseous fluid compartment, and subsequently after refilling the compartment with fluid. Drilling of the femoral head and disrupting its bony fluid compartment resulted in a 40% decrease in stiffness (P<.001). This effect was seen only with fresh specimens and not frozen specimens. Refilling the bony compartment with fluid restored the stiffness of the fresh femoral head. These results demonstrate the mechanical properties of trabecular bone in canine femoral head specimens in vitro are affected by intraosseous fluid and freezing. Removal of the intraosseous fluid decreases the mechanical stiffness of canine trabecular bone, and freezing the specimens appears to alter the intraosseous fluid compartment behavior. It is necessary to gain a better understanding of the dynamic mechanical properties of intact bone to improve the existing analytical and experimental mechanical bone models. The effect of intraosseous fluid and freezing should be considered in these models.

Cementless acetabular fixation in total hip arthroplasty using polyglycolide-lactide screws: an in vivo canine study

Bone ingrowth into cementless acetabular components was evaluated in a canine total hip arthroplasty model, comparing components initially stabilized with polyglycolide-lactide screws with those initially stabilized with titanium screws. The acetabular shell was anchored with 2 polyglycolide-lactide screws in 16 dogs and with 2 titanium screws in 12 dogs. The dogs were followed and sacrificed at 7 weeks, 14 weeks, 10 months, or 15 months. Histomorphometric analysis of bone ingrowth into the weight-bearing dome of the acetabular shell was conducted. No difference was detected in mean bone ingrowth into the acetabular shell comparing the 2 screw groups. The results of this study do not support a significant advantage to the use of biodegradable screws for the initial stabilization of cementless acetabular components in canine total hip arthroplasty.

A randomized trial of hydroxyapatite coated prostheses in total hip arthroplasty

In a prospective randomized trial, 62 consecutive primary cementless total hip arthroplasties in 55 patients were performed by one surgeon using either hydroxyapatite coated (35 hips) or nonhydroxyapatite coated femoral prostheses (27 hips). The dual tapered femoral stem had a Ti-6AI-4V plasma sprayed circumferential proximal porous coat applied to the proximal 1/3 of the stem. The middle 1/3 had a roughened blasted textured surface, and the distal 1/3 had a smooth surface. The hydroxyapatite coated femoral stems had an additional hydroxyapatite coating applied to the proximal porous coat with use of an air plasma process. The patients in the two groups were not significantly different regarding age (48.2 +/- 9.0 years hydroxyapatite group, 50.4 +/- 8.7 years control group), gender, Charnley class, or length of followup (4.4 +/- 0.7 years hydroxyapatite group, 4.9 +/- 1.0 years control group). Forty-nine patients (54 hips) were available for clinical followup, and 45 patients (50 hips) had radiographic followup. A minimum 3-year followup was recorded. To date, there have been no femoral prostheses failures. No femoral implant has migrated or subsided. Radiographically, the hydroxyapatite coated stems showed trends toward increased distal stem related cortical hypertrophy, increased cancellous condensation and less endosteal cavitation. Two nonhydroxyapatite coated stems had distal endosteal cavitation, whereas no hydroxyapatite coated stems did. There were two cases of acetabular osteolysis (revision in one) and two cases of acetabular cup migration (nonrevised), all occurring in the control group. The overall revision rate was 4%. There was no difference in Harris hip scores at 6 months (80.6 +/- 13.0 points hydroxyapatite group, 83.8 +/- 12.4 points control group) or at last followup (85.6 +/- 15.4 points hydroxyapatite group, 89.7 +/- 13.4 control group). The Harris hip pain scores also were not significantly different at 6 months or at last followup. Multiple linear regression analysis controlling for age, gender, and length of followup revealed no significant predictors of Harris hip or pain scores. The results of this study at an average of 4.6 years do not indicate a significant clinical advantage to the use of hydroxyapatite coated femoral prostheses in primary cementless total hip arthroplasty when judged by the criteria of Harris hip scores and femoral stem survivorship.

Use of a polyglycolide lactide cement plug restrictor in total hip arthroplasty

The use of a polyglycolide lactide cement plug restrictor in cemented femoral fixation during total hip arthroplasty was evaluated. Femoral cement pressurization was evaluated in vitro in a cadaveric model and the host response to polymer degradation was evaluated in vivo in a canine total hip arthroplasty model. Sixteen embalmed anatomic specimen femurs were prepared for cement femoral fixation. The intramedullary canal was plugged with either an ultrahigh molecular weight polyethylene cement plug restrictor or a polyglycolide lactide cement plug restrictor. Peak pressures in the proximal, mid, and distal portions of the cement mantle were recorded during cement insertion, cement pressurization, and implant insertion. There was no difference between the two plug groups in peak pressures throughout the cement mantle during cement insertion, pressurization, or implant insertion. Total hip arthroplasty using a cementless acetabular component and a cemented femoral stem was performed in 24 dogs. The femoral intramedullary canal was plugged with a polyethylene or a biodegradable cement plug restrictor. The dogs were sacrificed at 7 weeks, 10 months, or 15 months. Radiographically, no osteolytic lesions were seen around either plug type. Histomorphometrically, the polyglycolide lactide plugs appeared intact at 7 weeks and partially degraded by 10 and 15 months. In both plug groups, a mild fibrohistiocytic reaction with infiltration of fibrocytes, histocytes, and endothelial cells was seen. No osteolysis was observed. The results of the current study show that femoral cement pressurization can be attained in vitro using a biodegradable cement plug restrictor and that for as long as 15 months in the in vivo canine model there were no adverse reactions associated with use of these plugs compared with conventional ultrahigh molecular weight polyethylene plugs.

Total hip arthroplasty complicated by tuberculous infection

The case of a 66-year-old woman with tuberculous infection complicating a total hip arthroplasty that had been performed 4 years previously for degenerative arthritis is reported. The patient had no prior history of exposure to tuberculosis and no evidence of skeletal or nonskeletal tuberculous infection. The need for a high index of suspicion when dealing with unexpected arthroplasty failure is emphasized. Tuberculous cultures are recommended in these cases prior to revision surgery.

Choosing the socket in total hip arthroplasty

Significant improvements have been made in the long-term results of cemented femoral components, but there has been little improvement in the results of cemented acetabular components. Polyethylene wear debris has been proposed as the most important factor causing loosening of cemented acetabular components. Polyethylene thickness and femoral-head size affect the rate of acetabular wear and loosening. The early results of total hip arthroplasty with noncemented acetabular components are promising, and many feel that they represent the state of the art. The hemispheric components with a porous coating have proven superior to most of the screw ring designs. There are potential disadvantages with the use of screws to augment fixation of the hemispheric components, and recently it has become popular to under-ream the acetabulum and press-fit the oversized acetabular component without the use of screws.

The effect of the medial collar in total hip arthroplasty with porous-coated components inserted without cement. An in vivo canine study

We performed an in vivo study in a canine model to compare the results of the use of a porous-coated collared femoral component with those of the use of a porous-coated collarless femoral component in total hip arthroplasties without cement. Our study focused on the comparative proximal strain pattern, bone ingrowth, and cortical porosity of the two types of prostheses. We used a trochanteric wire marker to measure subsidence. The use of the limb was assessed with gait analysis. Twelve weeks after the operation, the collarless components had significantly greater bone ingrowth proximally (p = 0.003) and were associated with significantly lower cortical porosity (p = 0.006). There were no differences between the groups with regard to either axial or hoop strain. While the group that had a collarless prosthesis had significantly less proximal-medial radiolucency (p = 0.03), there were no differences between the groups with regard to subsidence.

Fixation with biodegradable devices of acetabular components in a canine model

Cementless total hip arthroplasty was performed in 13 dogs. The acetabular component was anchored with two biodegradable devices (polylactic acid) in seven dogs and with two titanium screws in six dogs. At 14 weeks, histomorphometric determinations of bony ingrowth into the porous coating of the acetabular weight bearing dome was 54.4% when fixed with the biodegradable devices and 58.9% when fixed with the titanium screws (no statistically significant difference; p = 0.556). At the sites of fixation, less bony ingrowth occurred with the biodegradable devices. The use of biodegradable devices in total hip arthroplasty should overcome the potential metal corrosion of titanium screws that can lead to polyethylene wear.

A comparison of the strength and stability of six techniques of cerclage wire fixation for fractures

An in vitro comparison of six methods of cerclage wire fixation was performed using 1-mm-diameter stainless steel wire. A testing apparatus was designed to simulate the tensile forces on a cerclage wire around a femoral shaft fracture. The hairpin cerclage knot that we describe generated significantly higher initial compressive force (p < 0.001) and had significantly higher tensile strength (p < 0.02) compared with the other five methods.

Femoral component offset. Its effect on strain in bone-cement

The magnitude of the offset of the femoral prosthesis strongly influences the mechanics of the hip following a total hip arthroplasty. An increased offset increases the moment arm of the abductor muscles. This reduces the abductor force required for normal gait and, consequently, reduces the resultant force across the hip joint. These factors are advantageous. However, increased offset also increases the bending moment on the implant, which could adversely increase the strain in the medial cement mantle. To evaluate the relative advantages and disadvantages of these conflicting results of increasing the offset of the femoral component the authors measured in vitro in cadaver femora the effect of differing offsets of the femoral component on strain in the cement mantle. After testing the intact femora, the authors cemented femoral prostheses in place and quantified the abductor force, resultant force, and strain in the cement mantle under loading conditions simulating single limb stance at different femoral offset levels. The reduction in both abductor and resultant force was substantial with increased femoral component offset, but the strain in the cement of the proximal medial portion of the cement mantle was not significantly increased.

Bead loosening from a porous-coated acetabular component. A follow-up note

Beaded porous-coated implants are commonly used in total joint arthroplasty. In this study, the authors extended the follow-up period for the Davey and Harris study of bead loosening in beaded cementless acetabular components. When 56 primary total hip arthroplasties were first reviewed, at an average of 2.5 years after surgery, the incidence of bead loosening was 8.9%. Reevaluation at a mean of 4.5 years after surgery revealed that the incidence of loosening had increased to 19.6%. Bead loosening was associated with acetabular migration in one component and a broken screw in a second. In the absence of loose beads, there were no broken fixation screws or socket migration. Radiolucencies at the bone-implant interface were seen in association with loose beads in only one case. Although long-term implications of bead loosening are not clear, bead migration may increase the possibility of macrophage response to metallic debris.

A preliminary report of the use of a cementless acetabular component with a cemented femoral component

A clinical and roentgenographic study was done on 52 primary total hip arthroplasties (THAs) in which all patients were treated with hip reconstruction with a combination of a cementless, porous-coated acetabular component and a cemented femoral component. The operations were performed between November 1982 and May 1984, and the patients were followed for an average of 31 months (range, 24-40 months). The average age of the patients (55 years) was younger than in many THA series. At the last follow-up assessment, 50 hips were classified as good or excellent, one as fair, and one as a poor result. No total hip component required revision. No acetabular components had migrated as judged by conventional roentgenographic examination, and only one hip had progressive radiolucencies around the acetabular component. No femoral component was rated definitely loose or probably loose, and only one was rated possibly loose. If long-term follow-up study confirms these preliminary results, the combination of a cemented femoral component with a cementless socket may prove to be of value for selected patients requiring THA.

Reverse skeletal traction for instability following revision total hip arthroplasty. A report of two cases

Dislocation is a recognized complication following total hip arthroplasty (THA). Immobilization of the hip has been used successfully to treat those cases due to soft-tissue laxity. In two patients who had severe instability of the hip following complex revision THA, skeletal traction through the tibia was applied in a cephalad direction for three weeks. This unique method of employing traction maintained a reduction and resulted in a stable hip at the six-month follow-up evaluation in both patients. Reverse skeletal traction is a valuable treatment option when more conventional methods of immobilization of the hip will not maintain a reduction due to soft-tissue compromise.

Loosening of cobalt chrome beads from a porous-coated acetabular component. A report of ten cases

Seventy consecutive total hip arthroplasties were performed using a porous-coated acetabular component consisting of a cobalt chrome substrate to which cobalt chrome beads were sintered. Fifty-six were primary arthroplasties and 14 were revisions. The authors analyzed the immediate postoperative roentgenographs of all 70 hips and the follow-up roentgenographs of the 66 hips that were followed for a minimum of two years, the average follow-up period being 30 months. Loose cobalt chrome beads were diagnosed in ten of the 70 hips (14.3%), five (8.9%) in the primary arthroplasties, and five (35.7%) in the revision arthroplasties. In two of the primary arthroplasties and three of the revision arthroplasties, the loose beads were observed on the immediate postoperative roentgenographs. None of the acetabular components appeared loose by other roentgenographic criteria. The sintering technique used in the manufacture of these implants did not prevent loosening of cobalt chrome beads from porous-coated cobalt chrome acetabular components. A longer follow-up period is required to assess fully the clinical significance.

Stability of ten configurations of the Hoffmann external-fixation frame

The rigidity, load to yield, and load to failure of ten configurations of the Hoffmann external fixator were investigated using a model of wooden pylons with a simulated fracture that consisted of either a reduced transverse cut or a ten-millimeter gap. The axial compressive, torsional, anterior-posterior bending, and medial-lateral bending characteristics of four forms of the single half-frame (half-pinned), four double half-frame, and two full-frame (transfixion-pinned) configurations were examined. Of the single half-frame configurations, a system with a second stacked connecting-rod proved to be superior; however, the system yielded at a mean axial compressive load of only 199 newtons and failed totally at 355 newtons. The delta frame (two rods connecting or triangulating two half-frames set at an angle of 45 degrees to one another) was as rigid as the quadrilateral full frame in axial compression; however, it exhibited low loads to yield and to failure, with means around 200 and 350 newtons, respectively. The use of only two pins in each pin-cluster did not significantly affect the performance of the delta frame. The two full-frame systems performed poorly in torsion and particularly poorly in anterior-posterior bending. The loads that caused a one-millimeter movement within the fracture gap in axial compression were notably low: for the stacked half-frames the load did not exceed a mean value of 174 newtons; for the double half-frame, 190 newtons; and for the quadrilateral frame, 412 newtons. We concluded that no frame had a good over-all performance with regard to rigidity.(ABSTRACT TRUNCATED AT 250 WORDS)

A biomechanical study of wire fixation

A biomechanical study of wire fixation was performed using 18-gauge stainless steel wire on an Instron universal testing machine. Six groups of wires were tested--an intact piece of wire (control), a wire bent to a right angle five times, a simple knot, a square knot, a loop knot and a twist knot. The tensile load-to-failure value for each wire was recorded. The intact wire broke at a mean load of 67 kg. The wires with the bend, the simple knot and the square knot all broke at similar loads. Those wires with a knot broke at the knot. The loop and the twist knots pulled apart at much lower loads. These results indicate that bending the wire does not weaken it substantially, but kinking may initiate the site of breakage. The square knot is the strongest knot; the loop and twist knots are not recommended if the wire is to be under tension.

A technique of posterior cervical fusion for instability of the cervical spine

A technique of posterior cervical spine fusion (the "Dewar procedure") that allows immediate stabilization of the spine requiring only minimal external support is described. The procedure was performed in 16 patients with unstable fractures or fracture-dislocations of the cervical spine. All patients went on to develop solid fusion. Twelve patients incurred neurologic deficit due to their injury, and those with root involvement all recovered following fusion. Patients rendered quadriplegic as a result of their accident did not show any useful neurologic recovery but were able to start rehabilitation earlier and avoid the complications of nonoperative treatment. There were no significant complications related to surgery.

The tibialis posterior muscle compartment. An unrecognized cause of exertional compartment syndrome

Exertional compartment syndrome in the deep posterior compartment of the leg is well recognized. This paper reports investigations which were performed to prove that the tibialis posterior muscle is contained in its own osseofascial compartment, separate from the rest of the deep posterior compartment. Radiographs following the injection of radio-opaque dye into the tibialis posterior muscle demonstrated the fluid-impermeable, osseofascial boundaries surrounding this muscle. Compartment syndromes created in cadaver legs reveal that traditional techniques of fasciotomy of the deep posterior compartment are inadequate in decompressing the tibialis posterior muscle. Intracompartmental pressure measurements in athletes with a clinical diagnosis of exertional compartment syndrome proved the existence of isolated exertional compartment syndrome in the tibialis posterior muscle. From these results we may conclude that the tibialis posterior muscle is contained in a separate osseofascial muscle compartment which may be the site of an isolated exertional compartment syndrome and that common techniques of fasciotomy of the deep posterior compartment do not decompress the tibialis posterior muscle.