Increased collection of patient-reported outcome measures (PROM) in registries enables international comparison of patient-centered outcomes after knee and hip replacement. We aimed to investigate 1) variations in PROM improvement, 2) the possible confounding factor of BMI, and 3) differences in comorbidity distributions between registries.

Registries affiliated with the International Society of Arthroplasty Registries (ISAR) or OECD membership countries were invited to report aggregate EQ-5D, OKS, OHS, HOOS-PS and KOOS-PS values. Eligible patients underwent primary total, unilateral knee or hip replacement for osteoarthritis within three years and had completed PROMs preoperatively and either 6 or 12 months postoperatively, excluding patients with subsequent revisions. For each PROM cohort, Chi-square tests were performed for BMI distributions across registries and 12 predefined PROM strata (male/female, age 20-64/65-74/>75, high or low preoperative PROM scores). Comorbidity distributions were reported for available comorbidity indexes.

Thirteen registries from 9 countries contributed data, n~130000 knee (range 140 to 79848) and n~113000 hip (range 137 to 85281). Mean EQ-5D index values (10 registries) ranged from 0.53 to 0.71 (knee) and 0.50 to 0.70 (hips) preoperatively and 0.78 to 0.85 (knee) and 0.83 to 0.87 (hip) postoperatively. Mean OKS (6 registries) ranged from 19.3 to 23.6 preoperatively and 36.2 to 41.2 postoperatively. Mean OHS (7 registries) ranged from 18.0 to 23.2 preoperatively and 39.8 to 44.2 postoperatively. Four registries reported KOOS-PS and three reported HOOS-PS. Proportions of patients with BMI >30 ranged from 35 to 62% (10 knee registries) and 16 to 43% (11 hip registries). For both knee and hip registries, distributions of patients across six BMI categories differed significantly among registries (p30 were for patients in the youngest age groups (20 to 64 and 65 to 74 years) with the lowest baseline scores. Additionally, females with lowest preoperative PROM scores had highest BMI. These findings were echoed for the OHS and OKS cohorts. Proportions of patients with ASA scores ≥3 ranged from 7 to 42% (9 knee registries) and 6 to 35% (8 hip registries).

PROM-score improvement varies between international registries, which may be partially explained by differences in age, sex and preoperative scores. BMI and comorbidity may be relevant to adjust for.

Introduction

CMS is now publicly reporting 30-day readmission rates following total joint replacement (TJR) by hospital and is planning the collection of patient-reported function and pain after TJR. Nationally, 5% of patients are readmitted to the hospital after TJR for both medical and orthopedic-related issues. However, the relationship between readmission and functional gain and pain relief after TJR has not been evaluated.

Summary Statement

In young, active patients cementless THR demonstrates excellent prosthetic stability by RSA and outstanding clinical outcomes at 5 years using a tapered titanium femoral stem, crosslinked polyethylene liners and either titanium or tantalum shells.

Summary Statement

For RA patients undergoing TKR, the gain in function at 6 months following surgery is less than that experienced by OA patients; for THR, however, gains are similar in OA and RA patients.

Summary Statement

A prospective randomised evaluation of primary TKA utilizing patient specific instruments demonstrated great accuracy of bone resection, improved sagittal alignment and the potential to improve functional outcomes and reduce operating room costs when compared to standard TKA instrumentation.

Summary Statement

This data may help explain the variability in physical function after primary TKR as compared to primary THR.

Introduction:

Total knee replacement (TKR) and total hip replacement (THR) reliably relieve pain, restore function, and ensure mobility in patients with advanced joint arthritis; however these results are not uniform across all patient populations. Moreover, it is well established that knee replacement patients have outcomes inferior to those undergoing hip replacement procedures with lower rates of dissatisfaction with post-operative function and pain relief.

We compared baseline demographic and symptom profiles in patients from a US national cohort undergoing primary TKR and THR to determine whether differences in demographic make-up, pre-operative symptoms, or pre-existing co-morbidities might contribute to these differences observed post-operatively.

Introduction:

There is an increasing trend within the US for utilization of total knee replacement for patients who are still of working-age. Numerous causes have been suggested, ranging from greater participation in demanding sporting activities to the epidemic of obesity. A universal concern is that increased arthritis burden will lead to increased disabilty and unsustainable health-care costs both now and in the future with increasing rates of revision surgery in the years ahead. This raises the critical question: Are younger patients receiving knee replacement prematurely? To address this issue, we compared the severity of operative knee pain and functional status in younger versus older TKR patients, drawing upon a national research registry.

Purpose

Arthritis is the most common chronic illness in the United States. TKR provides reliable pain relief and improved function for patients with advanced knee arthritis. Total joint replacement now represents the greatest expense in the national healthcare budget. Surgical costs are driven by two key components: fixed and variable costs. Patient Specific Instruments™ (PSI, Zimmer, Warsaw, IN, USA) has the potential to reduce both fixed and variable costs by shortening operative time and reducing surgical instrumentation. However, PSI requires the added costs of pre-operative MRI scanning and fabrication of custom pin guides. Previous studies have shown reduction in operating room times and required instrumentation, but question the cost-effectiveness of the technology. Also, these studies failed to show improvement in coronal alignment, but call for additional studies to determine any improvement in clinical function and patient satisfaction. Our pilot study aims to compare the incremental PSI costs to fixed and variable OR cost savings, and compare meaningful patient and clinical outcomes between PSI and standard TKR surgeries.

It has long been recognised that the periosteal membrane has osteogenic capability and experimental studies have concluded that periosteum transplanted to a distant site could also be osteogenic. This ability of periosteum to generate new bone at distant sites may have clinical application. In the laboratory setting however periosteal flaps in animals have demonstrated variable results. Little clinical work using the technique of periosteal transfer has been reported, with only individual case reports in the literature.

A clinical review of a series of three fracture patients in whom vascularised periosteal transfer has been used is presented. Cases involved a primary bony defect at the fracture site (first metatarsal), established non-union (tibia) or post-traumatic AVN (talar dome). The technique is described and clinical follow-up of the patients is presented.

In each instance evidence of lasting new bone formation was demonstrated clinically and radiologically.

The efficacy of this technique in forming new bone is demonstrated. The technique may have utility alongside other techniques in cases where new bone is required.

Introduction: Tumor necrosis factor-alpha (TNF-a) has been shown to be a potent stimulator of bone resorption in vitro and in vivo, and has been identified as an important factor in aseptic loosening of total joint replacements. In order to investigate the effects of TNF-a at the bone-cement interface, we developed a rabbit model in which a slow-release pellet containing a known amount of TNF-a was inserted adjacent to a polymethylmethacryate (PMMA) implant in the distal femur.

Methods: 25 male New Zealand white rabbits were used in this IACUC-approved study. After routine exposure of the distal femur, a 3 mm drill bit was used to drill through the intercondylar region into the medullary canal of the distal femur. A resorbable pellet containing 0, 420, 4200, 42 000 or 420 000 pg of TNF-a (n=5 animals per dose level) was inserted into the drill hole, immediately followed by a cylindrical PMMA implant (20 mm long). Animals were euthanized 42 days after surgery. The right femora were excised, radiographed, and processed for histology. Ground sections were prepared at the level of the proximal implant. Semi-automated image analysis was used to quantify cortical bone area, porosity and fractional surfaces (quiescent, osteoid and eroded). Data from control and treatment animals were compared with a one-way analysis of variance (ANOVA) using p< 0.05.

Results: All of the animals recovered well after surgery. Radiographically, all of the implants appeared to be stable, with no evidence of linear or cystic osteolysis. Local delivery of TNF-a for 6 weeks had no effect on cortical bone area or porosity. However, TNF-a stimulated bone resorption and decreased new bone formation at the endosteal surface (p< 0.05); these effects were not dose-dependent but were seen in all of the TNF-a groups.

Discussion: Our data provide direct evidence that local release of TNF-a is capable of inducing endosteal bone resorption in vivo. Additional studies are now needed to determine the effects of other proinflammatory cytokines in this animal model. However, based on these results, it appears that targeted blockade of TNF-a release or activity may provide a rational therapeutic approach to osteolysis and aseptic loosening.

There is little information available regarding mechanical aspects of cemented implant loosening and the initiation and development of cement damage. Previous studies have come to a variety of conclusions about the development of cement damage and the relative importance of voids, the stem/cement interface and the cement/bone interface.

Cement micro-cracks and stem/bone micro-motions were quantified for Charnley Cobra stems under “stair-climbing” loads. Six stem/cement/femur constructs were subjected to loads based on estimated body weight for 300 kcycles at 2 Hz; two additional constructs were not loaded. Transverse sections were cut at 10 mm intervals, stained with a fluorescent dye penetrant and examined using epifluorescence stereo-microscopy.

Despite the aggressive loading, all stem/bone micro-motions were small and all stems were “well fixed” at the end of the loading. The only consistent micro-motion was internal rotation but this did not significantly correlate with cement damage (p=0.9). For cyclically loaded constructs mean crack length was 0.49 mm (SD 0.37, range 0.07 to 4.42) and for non-loaded controls mean crack length was 0.25 mm (SD 0.18, range 0.03 to 1.16). Total crack length (46–281 mm) was significantly correlated (R2=0.819, p=0.002) with femoral head load (0 & 1.0–1.8 kN). There was a significantly (p< 0.05) greater proportion of damage at the cement/bone interface (66% ± 9) than at the stem/cement interface (28% ± 8). A small fraction of micro-cracks involved voids (5% ± 5), but these were significantly (p< 0.001) less than the cement/ bone fraction. Micro-cracks in unloaded specimens were evenly distributed axially (R2=0.0002, p=0.95) consistent with the theory that they were induced by cement shrinkage. ANCOVA for total crack density using head load and axial position as covariates showed a significant positive effect for head load (p< 0.0001) and a significant interaction between head load and axial position (p=0.001); under load, micro-crack density increased proximally, and this effect was stronger with increasing head load.

Highly polished femoral stems with a double taper have had outstanding long-term clinical results. Recently a stem with a third, cross-sectional taper was introduced with the goal of providing additional stability while still utilising the polished taper concept.

The goal of the present study was to determine if there were differences in the mechanical stability and cement damage due to cyclic loading of a triple-tapered (C-stem, J& J-DePuy) and a double-tapered design (TPS, J& J-DePuy). Six pairs of cadaveric femurs were cemented with either C-stem or TPS stems using contemporary techniques. Specimens were cyclically loaded using a stair-climbing apparatus with femoral head and abductor loads for 1 000 to 266 000 loading cycles. Motion between the stem and bone was measured using a 6 dof measurement system. Following testing, specimens were sectioned at four transverse levels and the number and length of cracks in the cement were measured.

All stems were extremely well fixed after loading. The C-stem did not subside during loading except for one outlier that was cemented ‘high’. The TPS stem had a pattern of rapid subsidence over the first 100 cycles (mean 0.032 mm) followed by a more gradual subsidence (0.05 mm at 266 k cycles). ANCOVA showed that the TPS-stems rotated significantly more than the C-stems (p< 0.0001), that the rotation of both stems increased with number of loading cycles (p=0.022) and that the effect of number of loading cycles was greater for the TPS stems (p=0.047). Total crack length was not a function of number of loading cycles, nor was it different for the two stem designs (p=0.33).

The outlier C-stem had micromotion behavior similar to the TPS stem. The reason for this is unclear, but could be due to reduced lateral-proximal cement. Thus it is possible that both the stem cross-sectional and in-plane shape contribute to the stability of the C-stem design.

The effect of pre-operative pain, physical function, mental function and multiple patient factors on patient outcome following TKR was examined.

After informed consent, 105 patients undergoing primary TKR completed preoperative SF-36 and WOMAC questionnaires and a Knee Society Score (KSS) was determined. These scores were repeated at 12 months. Patient data studied included age, gender, BMI and significant comorbid conditions such as diabetes, cardiac disease, and COPD. Statistical analysis included a univariate analysis, followed by a bivariate analysis and multiple regression analysis.

All physical dimensions of the SF-36, WOMAC and KSS showed highly significant improvements after one year. The KSS improved to a mean of 94.8 (p< 0.000001). For patients greater than 65 years of age, postoperative physical function was returned to normative scores for age matched controls. For patients less than 65, physical function did not reach age matched controls even though similar improvements in physical function were seen. Patients with lower physical function scores (PCS) pre-operatively showed greater improvement postoperatively yet did not reach the same absolute level of function as patients who had higher preoperative physical function. The mean PCS for men increased from 35 to 42, while for women it increased from 29 to 42 (p=0.042). Preoperative mental function (MCS) was a strong predictor of postoperative physical function. Patients with low preoperative MCS and one or more comorbid conditions were 10.1 times more likely to have a poor outcome following TKR.

Knowledge of preoperative physical function, mental function, gender, age and comorbid conditions improves prediction of post-operative physical function after TKR. Patients at high risk for little improvement following TKR are those with low preoperative mental function (MCS< 50) in addition to one or more comorbid conditions. These patients can be identified during the pre-operative period.

Bone-cement shrinkage has never been quantified in a stem/cement/femur construct. We observed gaps around femoral stems in transverse sections of stem/cement/femur constructs; a greater proportion of stem/cement (s/c) interface gaps were found around grit blasted sections of stems than satin finished sections. If s/c gap formation were a shrinkage artifact then mantles with few s/c interface gaps must manifest shrinkage elsewhere, at the c/b interface or voids. ‘Mould-gaps’ at a c/b interface have been described previously but not quantified. We analysed the area of gaps at both interfaces. We hypothesised 1) Total gap area was the same for all transverse sections. 2) Satin sections had greater c/b gap areas than grit sections.

Transverse sections of stem/cement/femur constructs were processed to highlight gap areas. Five stems had a satin finish (Ra 0.75 um) and five were proximally grit-blasted (Ra 5.3 um). Sections were coated with matt black spray paint and then polished with emery paper. This process left all interface gaps and voids filled with black paint, which facilitated digital imaging. Gaps were visually identified and measured using Image-Pro. Gap areas for each transverse section were normalised by the area of cement in that section.

Gaps were not evenly distributed; there was obvious localisation at both interfaces. No significant difference found between surface finishes in total gap area ((satin 3.1% ± 1.4):(grit 3.4% ± 1.5)), supporting our first hypothesis. S/c gap areas were significantly greater around grit blasted sections ((satin 0.1% ± 0.4):(grit 1.9% ± 1.7) p< 0.0001). C/b gap areas were significantly greater around satin finished sections ((satin 2.3% ± 1.3):(grit 1.0% ± 0.9) p< 0.0001), supporting our second hypothesis.

Shrinkage can localise into large interface gaps; which must lead to stress concentrations. C/b gaps are potentially benign as they can fill with bone. Cement failure at points of s/c contact would generate debris hindering bone formation.

Results are presented of a prospective audit of wound infection rates in patients undergoing surgery for hand injuries in a designated hand trauma day surgery unit. Hand trauma patients with suitable injuries referred from peripheral accident and emergency departments to the Hand Surgery Unit at Queen Victoria Hospital undergo surgery after a variable delay. Initial wound toilet is undertaken at referral and all patients are prescribed oral antibiotics while waiting up to five days for theatre.

Time to operation and results of microbiological wound swabs in theatre were correlated with post operative wound infection rates in fifty patients.

Initial analysis suggests little difference in subsequent wound infection rates between patients operated on within 48 hours and those delayed three to five days.