Lavage technique in total hip arthroplasty: jet lavage produces better cement penetration than syringe lavage in the proximal femur

Technical Properties and Biological Safety of Reprocessing Technique for a Handpiece of Disposable Pulsatile Lavage Device: An Experimental Study

Introduction

Bony surface cleaning using a pulse lavage device (PLD) is essential for modern cementation of hip and knee arthroplasties. This costly single-use device is a medical waste and unaffordable for some patients. Reprocessing is a worldwide standard strategy to solve this problem. To determine the technical properties and biological safety of a reprocessed PLD handpiece and compare its performance under different power supplies.

Materials and Methods

Eight brand-new disposable PLDs were tested for baseline technical properties (flow rate, pulse frequency, and peak pressure). Thereafter, they were reprocessed and retested for 10 rounds using two different power supplies. An adenosine triphosphate (ATP) swab test was performed on the PLD accessory parts after cleansing and disinfection. Passed-through isotonic sodium chloride solution ejected from the reprocessed PLD underwent aerobic bacterial culture. The unit costs of production were analysed.

Results

The mean flow rate of the disposable PLD (1.5±0.1 L/min) was less than that of reprocessed PLD using DC15V battery (2.5±0.3 L/min, p<0.001) and AC/DC15V3A adapter (6.1±0.4 L/min, p<0.001). The mean pulse frequency and peak pressure of the disposable PLD and reprocessed PLD using DC15V battery were not different (18.5±0.8 vs 18.8±2.5 Hz, p=0.155 and 0.37±0.04 vs 0.38±0.03 N/mm2, p=0.640, respectively), but were lower than those using AC/DC15V3A adapter (47.0±2.7 Hz, 0.45±0.03 N/mm2, p<0.001). All ATP swab tests, and aerobic fluid cultures yielded negative results. The total cost of reprocessing was 10% of disposable PLD.

Conclusion

A disposable PLD handpiece can be reprocessed without deteriorating its technical properties and used with either retrieved DC15V battery or AC/DC15V3A adapter for the power supply. As the biological safety of reprocessed and disposable PLDs was comparable, it may be clinically utilised with 90% cost reduction.

Reducing Carbon Footprint of Disposable Pulse Lavage Systems in Total Hip and Knee Arthroplasty

Pulse lavage is recommended in all modern total joint arthroplasty operations in the UK. The common current pulse lavage is a disposable battery-operated system. AC and power tool powered models are commercially available in the UK. We performed a carbon emissions analysis of each model to evaluate the reduction in the carbon footprint of the arthroplasty operations at one trust and extrapolated the data to scale the possible economic and environmental benefits. Introducing a power tool driven pulse lavage system can reduce the carbon footprint of pulse lavage by 50% compared to the battery and AC-powered options. Additionally, we have reduced the economic impact of one trust by switching to a "greener" alternative pulse lavage system. In trusts where a power tool-driven pulse lavage is not possible, we advocate using AC-powered kits that are less wasteful than the more commonly used battery-powered options.

Pulsatile lavage systems and their potential to penetrate soft tissue

BACKGROUND

In orthopedic and trauma surgery, pulsatile lavage systems are used to clean soft tissue. This may be necessary in septic surgeries or in case of contaminated wounds after trauma. Positive features such as reduction of bacterial contamination and removal of foreign particles are counterbalanced by negative aspects such as bacterial seeding in deeper tissue layers, damage to various tissues and even cases of air embolism.

PURPOSE

The aim of this prospective experimental in vitro study was to compare impact pressure and flow rate in three different pulsatile lavage systems and to determine, whether these parameters alter their ability to reach deeper soft tissue layers.

METHODS

To test the penetration of soft tissue, the muscle tissue was flushed with contrast medium instead of saline fluid and afterwards scanned by computed tomography.

RESULTS

Impact pressure and flow rate showed significant differences between the different systems. There were no significant differences between the three devices in terms of total penetration volume, but there were significant differences in penetration depth.

CONCLUSION

In this study, we found that higher impact pressure leads to deeper penetration and therefore bacteria are likely to be transferred to deeper tissue layers.

Femoral defects in revision hip arthroplasty: a therapy-oriented classification

INTRODUCTION

The complex field of femoral defects in revision hip arthroplasty displays a lack of standardized, intuitive pre- and intraoperative assessment. To address this issue, the femoral defect classification (FDC) is introduced to offer a reliable, reproducible and an intuitive classification system with a clear therapeutic guideline.

MATERIALS AND METHODS

The FDC is based on the integrity of the main femoral segments which determine function and structural support. It focuses on the femoral neck, the metaphysis consisting of the greater and lesser trochanter, and the femoral diaphysis. The four main categories determine the location of the defect while subcategories a, b and c are being used to classify the extent of damage in each location. In total, 218 preoperative radiographs were retrospectively graded according to FDC and compared to intraoperatively encountered bone defects. To account for inter-rater and intra-rater agreement, 5 different observers evaluated 80 randomized cases at different points in time.

RESULTS

A Cohens kappa of 0.832 ± 0.028 could be evaluated, accounting for excellent agreement between preoperative radiographs and intraoperative findings. To account for inter-rater reliability, 80 patients have been evaluated by 5 different observers. Testing for inter-rater reliability, a Fleiss Kappa of 0.688 could be evaluated falling into the good agreement range. When testing for intra-rater reliability, Cohens Kappa of each of the 5 raters has been analyzed and the mean was evaluated at 0.856 accounting for excellent agreement.

CONCLUSION

The FDC is a reliable and reproducible classification system. It combines intuitive use and structured design and allows for consistent preoperative planning and intraoperative guidance. A therapeutic algorithm has been created according to current literature and expert opinion. Due to the combination of the FDC with the recently introduced Acetabular Defect Classification (ADC) a structured approach to the entire field of hip revision arthroplasty is now available.

Direct Cementation of Dual Mobility Cups Into the Bony Acetabulum in Primary Total Hip Arthroplasty: Clinical and Radiographic Outcomes at a Minimum 5-Year Follow-Up

BACKGROUND

Cemented dual mobility cups (DMCs) are commonly used in combination with acetabular reinforcement devices. Indeed, according to literature, direct cementation of metal-backed acetabular components into the bony acetabulum remains controversial as this technique is potentially associated with increased rates of aseptic loosening. Therefore, this study aimed to evaluate the clinical and radiographic outcomes of DMC cemented into the bony acetabulum in primary total hip arthroplasty (THA).

METHODS

A total of 49 THA (48 patients, mean age 78 years [range, 51 to 91]) performed with direct cementation of a DMC into the bony acetabulum were prospectively included in our total joint registry and retrospectively reviewed. The clinical outcome was assessed using the Harris hip score (HHS). The radiographic outcome included measurement of component positioning and occurrence and progression of demarcation around the cemented DMC. Complications were reported with a particular attention to cemented fixation failure and aseptic loosening.

RESULTS

At a 7-year mean follow-up (range, 5 to 8), the pre-to postoperative HHS improved from 47 (range, 30 to 58) to 92 points (range, 80 to 98) (P < .01). Nonprogressive and focalized demarcations were observed in 7 THA (14%). Importantly, no progressive demarcation or DMC aseptic loosening was observed.

CONCLUSION

Direct cementation of DMC into the bony acetabulum ensured a stable fixation with no progressive demarcation or aseptic loosening at midterm follow-up. Therefore, this technique can be selectively considered in primary THA, especially in elderly or frail patients to avoid potential mechanical failure of press-fit fixation due to altered bone quality or additional morbidity related to the use of acetabular reinforcement devices.

The Cost-Effectiveness of Normal-Saline Pulsed Lavage for Infection Prophylaxis in Total Joint Arthroplasty

Background

Prosthetic joint infection (PJI) is a well-described complication after total joint arthroplasty which imposes a substantial burden of morbidity and mortality on the individual, as well as cost to the health-care system. This study used a break-even analysis to investigate the cost-effectiveness of pulsed saline lavage (PSL) for PJI prophylaxis after a primary total knee arthroplasty (TKA) and total hip arthroplasty (THA).

Methods

An established model was used to calculate the minimum cost-effective absolute risk reduction of PSL for infection prophylaxis after a total joint arthroplasty. Baseline infection rates of TKA and THA and the cost of a revision surgery for PJI were derived from the literature while the cost of PSL implementation was obtained from institutional data.

Results

PSL is cost-effective at an initial infection rate of 1.10%, revision costs of $32,132 for TKA PJI, and a protocol cost of $38.28 if it reduces infection rates by 0.12% or prevents infection in 1 out of 839 patients. PSL is cost-effective at an initial infection rate of 1.63% and a revision cost of $39,713 for THA PJI if it reduces infection rates by 0.10% or prevents infection in 1 out of 1037 patients. The absolute risk reduction needed for economic viability did not change with varying baseline infection rates and did not exceed 0.38% for infection treatment costs as low as $10,000 and remained less than 0.47% even if PSL cost was as high as $150.

Conclusions

The use of PSL is a cost-effective protocol for PJI prophylaxis after TKAs and THAs.

Femoral Stem Cementation in Primary Total Hip Arthroplasty

➢

Femoral stem cementation has undergone considerable investigation since bone cement was first used in arthroplasty, leading to the evolution of modern femoral stem cementation techniques.

➢

Although there is a worldwide trend toward the use of cementless components, cemented femoral stems have shown superiority in some studies and have clear indications in specific populations.

➢

There is a large evidence base regarding cement properties, preparation, and application techniques that underlie current beliefs and practice, but considerable controversy still exists.

➢

Although the cementing process adds technical complexity to total hip arthroplasty, growing evidence supports its use in certain cohorts. As such, it is critical that orthopaedic surgeons and investigators have a thorough understanding of the fundamentals and evidence underlying modern cementation techniques.

Bone cement implantation syndrome in hip arthroplasty: Frequency, severity and prevention

INTRODUCTION

Cemented femoral implants incur a serious risk of potentially fatal accidents in case of bone cement implantation syndrome (BCIS). As French data are sparse regarding this issue, Orthorisq, the official accreditation body for orthopedic surgeons, conducted an inter-professional survey: 1) to assess the frequency of BCIS, 2) to analyze risk factors related to the patient and to professional practices, and 3) to set out guidelines to reduce frequency and/or severity.

HYPOTHESIS

French data on BCIS are underestimated and need updating to ease communication between colleagues.

MATERIAL AND METHOD

In 2019, Orthorisq ran a survey of its members' practices and a "mirror" survey of anesthesiologists. In the decade from 2009 to 2018, the 775 respondent orthopedic surgeons, both occasional and systematic "cementers", reported their experience with a declared annual rate of 80,112 arthroplasties, including 63,799 (79.6%) in scheduled surgery. Some of the survey questions concerned cementing technique. With the help of the French College of Anesthesia and Intensive Care Medicine, 305 anesthesiologists responded to the mirror survey.

RESULTS

The 776 orthopedic surgeons reported 1896 cementing accidents with 387 deaths during the study decade. Accidents were 6-fold more frequent in traumatology than in scheduled orthopedic surgery (0.71% versus 0.12%) and, more importantly, were more serious: mortality was 10-fold higher (0.17% versus 0.017% [p<0.001]). Certain "tricks and tips" intended to improve cementing quality, such as a dedicated system and especially a plug, significantly increased the risk of BCIS (p<0.001). Over the same period, the 305 anesthesiologists had been involved in 490 cementing accidents; 88 (29%) had been faced by at least 1 death, most often in emergency settings (60/28). While 753 surgeons (96%) reported warning the anesthetists and 571 (74%) waited for agreement before cementing, only 109 (36%) and 124 (41%) anesthetists reported being systematically alerted to cementing and implant reduction, respectively. The rate of serious accidents was 0.19% and mortality was 0.05%, for a cumulative probability of 0.24% per year. Extrapolated to the data of the ATIH Technical Agency of Hospitalization Information and subtracting arthroplasties by "never-cementers", these figures indicate 311 accidents with 65 deaths in femoral BCIS for 2018.

DISCUSSION

In scheduled surgery, BCIS was exceptional, but the rate in traumatology was much higher. Certain techniques intended to improve femoral cementing quality actually increased the risk of BCIS; in high-risk patients, especially in traumatology, non-cemented femoral implants or else a 1st-generation cementing technique should therefore be preferred. Prevention of BCIS and/or reduction of severity require identification of at-risk patients and good communication between surgeons and anesthesiologists, especially at the various steps of the checklist.

LEVEL OF EVIDENCE

IV; case series.

Pulmonary cement embolism is frequently observed but not a contributing factor for death in patients with cemented total hip and knee arthroplasty: a postmortem study

Purpose

Bone cement is frequently used for implant fixation in orthopaedic surgery. The occurrence of pulmonary cement embolism (PCE) in hip and knee arthroplasty has been described previously, but the exact extent and frequency have not been adequately studied. A postmortem cohort provides a unique opportunity for a more detailed analysis of this phenomenon.

Methods

Through retrospective analysis of whole-body computed tomography (CT) scans and autopsy protocols, we identified 67 cases with previous cemented total hip or knee arthroplasties. A grading system originally developed for PCE after cemented spine procedures was used. Findings were compared with two control groups: 35 individuals with previous cementless total joint arthroplasty as well as 25 individuals without evidence of prostheses.

Results

PCE was detected in 46.3% of the cases: grade 1 (31.3%), grade 2 (10.5%), and grade 3 (4.5%). No statistically significant difference was found between hip and knee arthroplasties in terms of PCE frequency. Importantly, none of the autopsy reports listed PCE as a cause of death or a contributing factor for the patients’ death. In the two control groups, only one case per group was classified as grade 1 PCE, while the remaining cases did not show any evidence of PCE.

Conclusion

The presented data reveal a high frequency of PCE in hip and knee arthroplasties, which is almost identical to previous findings in patients with cement-augmented interventions in the spine. This way, our results underline the relevance of PCE after arthroplasty, suggesting an adaptation of surgical methods to minimize this complication.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00264-022-05381-6.

Does Additive Pressurized Carbon Dioxide Lavage Improve Cement Penetration and Bond Strength in Cemented Arthroplasty?

The modern cementing technique in cemented arthroplasty is a highly standardized and, therefore, safe procedure. Nevertheless, aseptic loosening is still the main reason for revision after cemented total knee or cemented total hip arthroplasty. To investigate whether an additional carbon dioxide lavage after a high-pressure pulsatile saline lavage has a positive effect on the bone-cement interface or cement penetration, we set up a standardized laboratory experiment with 28 human femoral heads. After a standardized cleaning procedure, the test implants were cemented onto the cancellous bone. Subsequently, the maximum failure load of the bone-cement interface was determined using a material testing machine to pull off the implant, and the cement penetration was determined using computed tomography. Neither the maximum failure load nor cement penetration into the cancellous bone revealed significant differences between the groups. In conclusion, according to our experiments, the additive use of the carbon dioxide lavage after the high-pressure pulsatile lavage has no additional benefit for the cleaning of the cancellous bone and, therefore, cannot be recommended without restrictions.

Cessation of Pulsed Lavage During the SARS-CoV-2 Pandemic: The Effect on Hip Hemiarthroplasty Cement Mantles

Background With the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, we were issued with guidance to minimize aerosol-generating procedures and discontinued the use of pulsed lavage for hip hemiarthroplasty. Instead, we used a bladder syringe to wash the femoral canal. The aim of this study was to assess whether this change in practice had a detrimental effect on the quality of the bone cement mantles in patients undergoing cemented hip hemiarthroplasty. Methodology We performed a retrospective review of all patients treated at a tertiary teaching hospital in the United Kingdom (Addenbrookes, Cambridge University Hospitals) presenting with a neck of femur fracture requiring a hemiarthroplasty between October 2019 and June 2020. We retrospectively assessed 100 post-operative radiographs for patients who had received hip hemiarthroplasty following neck of femur fragility fracture (50 before the service change and 50 after). The Barrack classification was used to assess the quality of the bone cement mantle. Results Pre-SARS-CoV-2, 30% of hemiarthroplasties were deemed as being "at risk" of aseptic loosening. During SARS-CoV-2, 64% of hips were deemed as being "at risk." This represents a statistically significant absolute increase of 34% (P < 0.05, the P value is 0.000645). Both clinicians agreed on the classification of hips "at risk" or "not at risk" (i.e., grades C/D and A/B, respectively) in 85% of the cases. Cohen's kappa coefficient was calculated as 0.68, indicating substantial agreement. Conclusions Following our experience of this forced service change, we would discourage abandoning the use of pulsed lavage in future pandemics. We have demonstrated an association between abandoning pulsed lavage and detrimental effects on the procedural quality for hip hemiarthroplasty. Patients treated over this time period will be closely monitored for operative complications. As this was the only equipment change made for this procedure, we have demonstrated its detrimental effect on the procedural quality. Should pulsed lavage be discontinued, patients may need to be counseled for higher risk of early failure and revision surgery and may require long-term radiographic follow-up. In SARS-CoV-2-positive patients, Surgeons should carefully consider the risks and benefits of using pulsed lavage in accordance with the personal protective equipment they have available and the consequential impact on the bone cement mantle quality.

No effect of femoral canal jet-lavage on the stability of cementless stems in primary hip arthroplasty: a randomised RSA study with 6 years follow-up

INTRODUCTION

In contrast to cemented hip prostheses, the effect of washing the bone bed with jet-lavage prior to insertion of cementless stem components in primary hip arthroplasty (THA) is unclear. Jet-lavage potentially decreases the risk of fat embolisation during rasping and stem insertion and might help in avoiding bacterial contamination. An earlier animal study has shown less debris and better-organised trabecular structure of new bone when jet-lavage was used. We hypothesised that the primary stability of cementless femoral stems implanted after jet-lavage of the femoral canal prior to stem insertion would improve with earlier stabilisation, as measured with Radiostereometry (RSA), compared with insertion without prior jet-lavage.

METHODS

40 patients with primary osteoarthritis operated on with a cementless titanium grit blasted stem are included in the study. The patients were randomised to either jet-lavage or control without any lavage of the femoral canal prior to insertion of the prosthesis. The stem migration pattern was measured with RSA at 0, 3, 12, 24 and 72 months.

RESULTS

At 6 years, 19 patients remained for analysis in the jet-lavage and 18 in the control group. We found no difference in extent or pattern of migration as measured with RSA. Both groups seemed to have stabilised within 3 months after a slight subsidence and retroversion. No stem was revised or considered loose as measured with RSA.

CONCLUSIONS

Washing the bone bed with jet-lavage prior to insertion of cementless stems does not affect the stability of cementless femoral components. No adverse effects were observed.

Current concepts and outcomes in cemented femoral stem design and cementation techniques: the argument for a new classification system

Cemented implant fixation design principles have evolved since the 1950s, and various femoral stem designs are currently in use to provide a stable construct between the implant-cement and cement-bone interfaces.Cemented stems have classically been classified into two broad categories: taper slip or force closed, and composite beams or shaped closed designs. While these simplifications are acceptable general categories, there are other important surgical details that need to be taken into consideration such as different broaching techniques, cementing techniques and mantle thickness.With the evolution of cemented implants, the introduction of newer implants which have hybrid properties, and the use of different broaching techniques, the classification of a very heterogenous group of implants into simple binary categories becomes increasingly difficult. A more comprehensive classification system would aid in comparison of results and better understanding of the implants' biomechanics.We review these differing stem designs, their respective cementing techniques and geometries. We then propose a simple four-part classification system and summarize the long-term outcomes and international registry data for each respective type of cemented prosthesis. Cite this article: EFORT Open Rev 2020;5:241-252. DOI: 10.1302/2058-5241.5.190034.

Water Jet Applicator for Interface Tissue Removal in Minimally Invasive Hip Refixation: Testing the Principle and Design of Prototype

Mechanical loosening of implants is in the majority accompanied with a periprosthetic interface membrane, which has to be removed during revision surgery. The same is true if a minimal invasive (percutaneous) refixation of a loose implant is done. We describe the requirements for a waterjet applicator for interface tissue removal for this percutaneous hip refixation technique. The technical requirements were either obtained from a literature review, a theoretical analysis, or by experimental setup. Based on the requirements, a waterjet applicator is designed which is basically a flexible tube (outer diameter 3 mm) with two channels. One channel for the water supply (diameter 0.9 mm) and one for suction to evacuate water and morcellated interface tissue from the periprosthetic cavity. The applicator has a rigid tip (length 6 mm), which directs the water flow to create two waterjets (diameter 0.2 mm), both focused into the suction channel. The functionality of this new applicator is demonstrated by testing a prototype of the applicator tip in an in vitro experimental setup. This testing has shown that the designed applicator for interface tissue removal will eliminate the risk of water pressure buildup; the ejected water was immediately evacuated from the periprosthetic cavity. Blocking of the suction opening was prevented because the jets cut through interface tissue that gets in front of the suction channel. Although further development of the water applicator is necessary, the presented design of the applicator is suitable for interface tissue removal in a minimally invasive hip refixation procedure.

Bone cement usage modalities at a multi-site university hospital centre

BACKGROUND

Although cements are widely used during arthroplasty procedures, few recommendations exist regarding their optimal usage modalities, which, nevertheless, govern the long-term surgical outcomes. No detailed information is available on how cements are used in French hospitals. The objectives of this questionnaire survey among surgeons working at a multi-site university hospital in France were to describe practices, determine whether these varied with surgeon experience, and look for differences compared to recommendations.

HYPOTHESIS

Cementing techniques vary widely among surgeons at a university hospital.

MATERIAL AND METHODS

A questionnaire was sent to the five orthopaedic departments of our university hospital to collect data on the surgeons (age, sex, years of experience), their practice (type of implants used, annual number of arthroplasties with each arthroplasty type and each indication, and proportion of cemented arthroplasties), the type of cement used, and the cementing technique.

RESULTS

Of the 34 surgeons, 21 completed the questionnaire, 20 males and 1 female with a mean age of 41 years (range, 31-59 years) and a mean of 11 years (range, 1-29 years) of experience. High-viscosity antibiotic-loaded cement was preferred by 20 (95%) surgeons, notably for knee arthroplasties, of which the median annual numbers were 55 (range, 0-218) and 8 (range, 1-40) for primary and revision cemented procedures, respectively. Various cementing techniques in ambient air were used: 12/21 (57%) surgeons used pulsed lavage to prepare the bone before cementation and 18/21 (86%) applied the cement to both the bone cuts and the implant. Of the 18 surgeons who performed knee arthroplasties, 12 used pulsed lavage, including 9 of the 11 surgeons with more than 5 years of experience and only 3 of the 7 less experienced surgeons. Similarly, of the 12 surgeons who used pulsed lavage for cemented arthroplasties, 11 were among the 12 surgeons who performed more than 15 cemented arthroplasties annually and 1 was among the 6 who performed fewer cemented arthroplasties.

DISCUSSION

Cementing techniques varied widely, reflecting the dearth of recommendations and controversial results of published studies. In our centre, the use of pulsed lavage to improve bone preparation and cement application to both the bone and the implant should be promoted, as both techniques are universally advocated. Our study demonstrates the need to provide surgeons with opportunities to exchange their experiences about the other aspects of cementing in order to harmonise practices and to optimise the use of cement.

LEVEL OF EVIDENCE

IV, questionnaire survey.

The protective effect of pulsed lavage against implant subsidence and micromotion for cemented tibial unicompartmental knee components: an experimental cadaver study

Cemented UKAs were performed in 12 pairs of human cadaver legs and the bone bed was cleansed using pulsed lavage (group A) and conventional syringe lavage (group B). Subsidence and micromotion of the loaded tibial trays were measured. There was a significant effect of BMD on subsidence (P = 0.043) but not on micromotion. Cement penetration of group A was significantly increased (P = 0.005). Group A showed a reduced implant subsidence (P = 0.025) and micromotion (P = 0.026) compared to group B. The group differences in micromotion and implant subsidence of UKA tibial components were statistically significant but rather small and might clinically be of minor importance. Nevertheless a worse bone quality adversely affected implant subsidence and pulsed lavage had a protective effect in these specimens.

The Basis CL cemented femoral stem: results after 8.9 years follow-up

This prospective study was conducted to demonstrate that the matte-finish Basis CL cemented endoprosthetic stem delivers good qualitative results after 10 years. Between January and December 1999, 205 consecutive hips (201 patients; 74.5 ± 6.8 years at surgery) underwent primary total hip arthroplasty with the Basis CL and the same acetabular cup (RM Classic cup) at a single institution. Follow-up data at 10 years was available for 120 hips (average follow-up of 8.9 years, ±2.9). Mean Harris Hip Score improved from 39.5 ± 16.8 at baseline to 75.9 ± 16.7 at 10-year follow-up (p<0.001). Four hips required revision during the study: three for infection and one for pain. There were no cases of aseptic loosening, implant migration, or stem fracture. Cumulative survival at 10 years was 97.4% with the endpoint of revision for any reason. In conclusion, results with the matte-finish cemented Basis CL indicated that it was safe and effective after medium-term follow-up.

Bone cement

The knowledge about the bone cement is of paramount importance to all Orthopaedic surgeons. Although the bone cement had been the gold standard in the field of joint replacement surgery, its use has somewhat decreased because of the advent of press-fit implants which encourages bone in growth. The shortcomings, side effects and toxicity of the bone cement are being addressed recently. More research is needed and continues in the field of nanoparticle additives, enhanced bone-cement interface etc.

Short-keeled cemented tibial components show an increased risk for aseptic loosening

BACKGROUND

The choice of implant design plays an important role for primary fixation of a TKA. Short-keeled tibial components allow implantation through a smaller approach with less femorotibial subluxation.

QUESTIONS/PURPOSES

The purpose of this study was to detect early implant failure resulting from aseptic loosening after cemented short-keeled and standard tibial baseplate implantation.

METHODS

Between 2008 and 2010, a group of 160 consecutive patients (with 80 standard and with 80 short-keeled tibial trays) received cemented TKAs. At 1-year followup, patients were examined clinically and radiographs were analyzed regarding aspects of radiolucency. The components were divided into five zones on each radiographic view and the measurements of the 10 zones were added.

RESULTS

The mean sum of radiolucencies was increased significantly with the short-keeled baseplates. In the current study, short-keeled tibial trays revealed a revision rate of 6.3% after 1-year followup. In contrast, none of the standard tibial baseplates were revised.

CONCLUSIONS

The implantation of cemented, short-keeled tibial components is linked to an increased rate of early loosening. Therefore, the indication for cemented, short-keeled component implantation should be reviewed.

LEVEL OF EVIDENCE

Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

The effect of bone lavage on femoral cement penetration and interface temperature during Oxford unicompartmental knee arthroplasty with cement

BACKGROUND

Aseptic loosening is the most common cause for revision unicompartmental knee arthroplasty and is associated with failure of the bone-cement or cement-implant interface. The purpose of the present study was to analyze different bone lavage techniques for the bone-cement and cement-implant interfaces of the femoral component and to study the effect of these techniques on cement penetration and on interface temperature.

METHODS

In an experimental cadaver study, Oxford unicompartmental knee arthroplasty was performed in twenty-four matched-paired knees to study the effect of pulsed lavage compared with syringe lavage on femoral cement penetration and interface temperature. Interface temperature, cement penetration pressure, and ligament tension forces were measured continuously during the procedure, and cement penetration was determined by performing sagittal bone cuts.

RESULTS

Cleansing the femoral bone stock with use of pulsed lavage (Group B) led to increased femoral cement penetration (mean, 1428 mm²; 95% confidence interval, 1348 to 1508 mm²) compared with syringe lavage (Group A) (mean, 1128 mm²; 95% confidence interval, 1038 to 1219 mm²) (p < 0.001). Interface temperature was higher in Group B (mean 22.6°C; 95% confidence interval, 20.5°C to 24.1°C) than in Group A (mean, 21.0°C; 95% confidence interval, 19.4°C to 23.0°C) (p = 0.028), but temperatures never reached critical values for thermal damage to the bone.

CONCLUSIONS

Pulsed lavage leads to an increased femoral cement penetration without the risk of heat necrosis at the bone-cement interface.

Tibial cleaning method for cemented total knee arthroplasty: An experimental study

BACKGROUND

The survival rate of cemented knee prosthesis depends among other factors on optimal cement-bone contact, nevertheless no standard exists for cementing technique of tibial components. The aim of this study was to determine which tibial surface preparation technique leads to the best bone-cement contact.

MATERIALS AND METHODS

HUMAN TIBIAL PLATEAU SPECIMENS WERE CLEANED IN FOUR DIFFERENT WAYS BEFORE CEMENTING: a) no cleaning, b) manual syringe irrigation, c) fracture brush cleaning, and d) pulsatile jet-lavage. The specimens were cut into transverse sections and the bone cement contact distance was calculated for every 10 mm and the cement penetration depth was measured. Both values were statistically analyzed (ANOVA).

RESULTS

The longest bone-cement contact (62 mm) was seen after PJL, the shortest (10.6 mm) after no cleaning at all. The deepest cement penetration (4.1 mm) again was seen after PJL, the least (0.7 mm) after no cleaning. Statistically, PJL yielded the longest bone-cement contact and deepest cement penetration.

CONCLUSION

The results supports the use of pulsatile jet-lavage before cementing tibial components in knee arthroplasty.

Radiofrequency-targeted vertebral augmentation versus traditional balloon kyphoplasty: radiographic and morphologic outcomes of an ex vivo biomechanical pilot study

PURPOSE

Traditional balloon kyphoplasty (BK) is a common treatment for symptomatic vertebral compression fractures. The purpose of this study was to compare a novel vertebral augmentation technique, radiofrequency-targeted vertebral augmentation (RF-TVA), to BK for restoration of vertebral height, cavity creation, and polymethylmethacrylate (PMMA) delivery and interdigitation into the surrounding trabeculae.

METHODS

This ex vivo biomechanical pilot study utilized 16 osteoporotic cadaveric vertebral bodies in a standardized fracture model to compare unipedicular RF-TVA (n = 8) to bipedicular BK (n = 8). Four specimens from each group were tested in loaded and unloaded conditions. All specimens were imaged, assessed for height restoration, and sectioned to observe PMMA distribution. A subset of specimens underwent computed tomography scanning to assess cavity creation and trabecular architecture prior to cement delivery.

RESULTS

Anterior height restoration was greater with RF-TVA (median: 84%, interquartile range: 62%-95%) compared to BK (median: 69%, interquartile range: 60%-81%), although the difference did not achieve statistical significance (P = 0.16). Anterior height restoration was numerically greater under loaded (median: 70% versus 66%) and unloaded (median: 94% versus 77%) conditions with RF-TVA versus BK. RF-TVA produced more discrete cavities and less native trabecular destruction compared to marked trabecular destruction observed with BK. RF-TVA consistently showed a well-identified focal area of PMMA with an extensive peripheral zone of PMMA interdigitation, providing mechanical interlock into the adjacent intact trabecular matrix. In contrast, BK yielded little evidence of PMMA interdigitation beyond the boundaries created by the balloon tamp due to the crushed trabecular bone peripherally.

CONCLUSION

RF-TVA achieves favorable vertebral height restoration with targeted PMMA delivery and less trabecular destruction compared to BK. RF-TVA has potential clinical utility in the aging population with painful osteoporotic vertebral fracture.

Noise-enhanced clustering and competitive learning algorithms

Noise can provably speed up convergence in many centroid-based clustering algorithms. This includes the popular k-means clustering algorithm. The clustering noise benefit follows from the general noise benefit for the expectation-maximization algorithm because many clustering algorithms are special cases of the expectation-maximization algorithm. Simulations show that noise also speeds up convergence in stochastic unsupervised competitive learning, supervised competitive learning, and differential competitive learning.

Secondary cement injection technique reduces pulmonary embolism in total hip arthroplasty

PURPOSE

Cardio-pulmonary damage due to embolism is a feared complication of cemented hip arthroplasty and can be fatal. Embolic events result from an increased intramedullary pressure during cement and stem insertion and can lead to extrusion of bone-marrow elements into the circulation. To reduce embolism and at the same time achieve an ideal cement mantle, the cement injection stem has been designed. In contrast to conventional stems where cement applied before stem insertion (primary cementing technique), the cement injection stem is positioned first and only then is the cement injected via the stem in a volume- and pressure-controlled fashion (secondary cementing technique).

METHODS

A randomised trial with 30 patients was performed to evaluate whether this technique is able to reduce embolic events. Patients either received a conventional cemented stem (primary cementing technique) or a cement injection stem (secondary cementing technique). Embolic events were recorded by transesophageal echocardiography at six specific points during the operation and classified from grade 0 to grade 3.

RESULTS

Significantly fewer grade 2 and 3 embolic events were observed in patients receiving the cement injection stem using the secondary cementing technique. Moreover, in the conventional group all patients (100 %) had at least one grade 3 embolus whereas only 20 % with the secondary cementing technique had an embolic event of grade 3.

CONCLUSION

Secondary cement insertion via the cement injection stem is able to reduce severe embolic events significantly. The technique offers a more gentle cementing technique and therefore appears especially beneficial for patients of advanced age and/or with pre-existing cardio-pulmonary comorbidities.

Bone-cement interface strength in distal radii using two medullary canal preparation techniques: carbon dioxide jet cleaning versus syringed saline

PURPOSE

Loosening is an important cause of failure of upper limb arthroplasty and improvement in cementation techniques may limit this. The currently accepted medullary canal preparation techniques use saline washing and gauze drying. Another method of bone preparation uses carbon dioxide compression gas jet which blows debris from the canal, whilst simultaneously drying the bone. We compared the push out strengths of cement plugs in sections of human cadaveric radii that had been prepared using either syringed saline or carbon dioxide jet cleaning.

METHODS

Following bone preparation, four radii in each group, were cemented in a standardised fashion, and cut into 1 cm sections. An Instron materials testing machine was used to measure the force needed to push the cement plug out of the bone section.

RESULTS

The force needed to push out the cement plug was significantly higher in the carbon dioxide jet (median 580.61, IQR 429.10-650.05) as compared to the saline group (median 366.57N, IQR 271.05-502.23), P = 0.009. The mechanism of failure of the bone-cement interface also differed between the two groups, with 100% of the sectioned cortices fracturing prior to cement extrusion in the carbon dioxide jet group, but only 23% of the sectioned cortices doing so in the saline group.

CONCLUSION

Our results suggest that there is a statistically stronger macro-interlock at the bone-cement interface after preparation of the medullary canals of radii using a carbon dioxide compression gas jet as compared to saline irrigation.

Pulsed lavage improves fixation strength of cemented tibial components

Pulsatile lavage is purported to improve radiographic survival in cemented total knee arthroplasty (TKA). Similarly, a potential improvement of fixation strength of the tibial tray has been assumed based on the increased cement penetration. In this study, the influence of pulsed lavage on fixation strength of the tibial component and bone cement penetration was evaluated in six pairs of cadaveric specimens. Following surgical preparation, the tibial surface was irrigated using pulsatile lavage on one side of a pair, while on the other side syringe lavage was applied. All tibial components were implanted using the same cementing technique. Cement penetration and bone mineral density was assessed based on computed tomography data. Fixation strength of the tibial trays was determined by a pull-out test with a material testing machine. Median pull-out forces and cement penetration were significantly (p = 0.031) improved in the pulsed lavage group as compared to the syringe lavage group. Enhanced fixation strength is suggested as being a key to improved survival of the implant. Consequently, pulsatile lavage should be considered as a mandatory preparation step when cementing tibial components in TKA.

Basic science considerations in primary total hip replacement arthroplasty

Total Hip Replacement is one of the most common operations performed in the developed world today. An increasingly ageing population means that the numbers of people undergoing this operation is set to rise. There are a numerous number of prosthesis on the market and it is often difficult to choose between them. It is therefore necessary to have a good understanding of the basic scientific principles in Total Hip Replacement and the evidence base underpinning them. This paper reviews the relevant anatomical and biomechanical principles in THA. It goes on to elaborate on the structural properties of materials used in modern implants and looks at the evidence base for different types of fixation including cemented and uncemented components. Modern bearing surfaces are discussed in addition to the scientific basis of various surface engineering modifications in THA prostheses. The basic science considerations in component alignment and abductor tension are also discussed. A brief discussion on modular and custom designs of THR is also included. This article reviews basic science concepts and the rationale underpinning the use of the femoral and acetabular component in total hip replacement.

Pulse-lavage brushing followed by hydrogen peroxide-gauze packing for bone-bed preparation in cemented total hip arthroplasty: a bovine model

PURPOSE

To compare the effectiveness of pulse-lavage brushing followed by hydrogen peroxide-gauze packing with either technique alone or normal-saline irrigation in bone-bed preparation for cemented total hip arthroplasty.

METHODS

44 fresh-frozen ox femoral canals were prepared for cemented total hip arthroplasty using 4 techniques: normal-saline irrigation, pulse-lavage brushing, hydrogen peroxide-soaked gauze packing, and a combination of the latter 2 techniques. The maximum tensile pull-out force required to separate the prosthesis from the femoral canal was measured as an indicator of the strength of the cement-bone interface.

RESULTS

The mean pull-out force to separate the prosthesis from the femoral canal was significantly higher in specimens prepared with pulse-lavage brushing followed by hydrogen peroxide-soaked gauze packing or pulse-lavage brushing alone than those prepared with normal-saline irrigation or hydrogen peroxide-soaked gauze packing alone (p<0.001).

CONCLUSIONS

Pulse-lavage brushing is more effective at cleansing the femoral canal and increasing mechanical strength at the cement-bone interface than preparation with normal-saline irrigation or hydrogen peroxide-soaked gauze packing.

Acetabular cementing technique in THA—flanged versus unflanged cups, cadaver experiments

BACKGROUND

There are few studies on the effect of acetabular cup design on cement penetration.

MATERIAL AND METHODS

We evaluated the effects of an acetabular flange on cement pressurization and cement penetration in 12 cadavers. Flanged or unflanged cups were implanted in paired human acetabula with simulated intraosseous bleeding pressure but without cement pressurization before insertion of the cup. Three pressure transducers were used to record intra-acetabular peak and average pressures during cup insertion. Following implantation, the whole specimens were AP-radiographed and standardized sections through the acetabula were microradiographed to evaluate cement penetration.

RESULTS

Flanged cups produced greater intra-acetabular peak pressures than unflanged cups, but did not increase the average intra-acetabular pressure. Cement penetration did not differ significantly between the two groups.

INTERPRETATION

Our findings do not support the use of flanged cups as the sole means of cement pressurization in the acetabulum.

Contemporary cementing technique and mortality during and after Exeter total hip arthroplasty

The Exeter universal stem implanted with contemporary cementing technique has shown an excellent survivorship at 15 years. The technique used for implantation calls for prolonged pressurization preventing blood from the femur exiting into the femoral canal, but this technique is not accepted widely as some surgeons believe it is associated with significant morbidity. This concern prompted this review. From 1988 to 2005, 9082 primary total hip arthroplasty (THA) were implanted. We identified all patients who died within 30 days from surgery. When available, the postmortem results were reviewed. Twenty-one patients died within 30 days from their primary THA (prevalence, 0.23%). There was one intraoperative death (prevalence, 0.01%). The postmortem report was consistent with fat embolism. Two additional patients died the same day of surgery from cardiac processes. No other deaths could be linked to cement. Sudden death during cemented THA with a current contemporary cementing technique and a specialized anesthetic protocol is nearly zero.

Pulsed lavage reduces the incidence of radiolucent lines under the tibial tray of Oxford unicompartmental knee arthroplasty: pulsed lavage versus syringe lavage

The aim of the study was to determine whether the incidence of radiolucencies can be reduced using pulsed lavage before cementing the tibia in unicompartmental knee arthroplasty (UKA). We prospectively studied a consecutive series of 112 cemented Oxford UKA in 100 patients in two centres. In group A (n = 56) pulsed lavage and in group B (n = 56) conventional syringe lavage was used to clean the cancellous bone. The same standardised cementing technique was applied in all cases. At a minimum follow-up of one year patients were evaluated clinically and screened radiographs were obtained. The cement bone interface under the tibial plateau was divided into four zones and evaluated for the presence of radiolucent lines. All radiographs were evaluated (n = 112), and radiolucencies in all four zones were found in two cases in group A (4%) and in 12 cases in group B (22%) (p = 0.0149). Cement penetration showed a median of 2.6 mm (group A) and 1.5 mm (group B) (p < 0.0001). We recommend the routine use of pulsed lavage in Oxford UKA to reduce the incidence of radiolucency and to improve long-term fixation.

Cement penetration after patella venting

There is a high rate of patellofemoral complications following total knee arthroplasty. Optimization of the cement-bone interface by venting and suction of the tibial plateau has been shown to improve cement penetration. Our study was designed to investigate if venting the patella prior to cementing improved cement penetration. Ten paired cadaver patellae were allocated prior to resurfacing to be vented or non-vented. Bone mineral density (BMD) was measured by DEXA scanning. In vented specimens, a 1.6 mm Kirschner wire was used to breach the anterior cortex at the center. Specimens were resurfaced with standard Profix instrumentation and Versabond bone cement (Smith and Nephew PLC, UK). Cement penetration was assessed from Faxitron and sectioned images by a digital image software package (ImageJ V1.38, NIH, USA). Wilcoxon rank sum test was used to assess the difference in cement penetration between groups. The relationship between BMD and cement penetration was analyzed by Pearson correlation coefficient. There was a strong negative correlation between peak BMD and cement penetration when analyzed independent of experimental grouping (r(2)=-0.812, p=0.004). Wilcoxon rank sum testing demonstrated no significant difference (rank sum statistic W=27, p=0.579) in cement penetration between vented (10.53%+/-4.66; mean+/-std dev) and non-vented patellae (11.51%+/-6.23; mean+/-std dev). Venting the patella using a Kirschner wire does not have a significant effect on the amount of cement penetration achieved in vitro using Profix instrumentation and Versabond cement.

An experimental comparison of different devices for pulsatile high-pressure lavage and their relevance to cement intrusion into cancellous bone

INTRODUCTION

Some of the systems marketed for pulsatile high-pressure lavage are clearly different in their mechanical pulse characteristics. To take the matter further we set up an experimental in vitro model to determine whether these different lavage systems might produce different cementation results because of their differing pulse characteristics, and whether the systems differed significantly in terms of cement depth penetration.

MATERIALS AND METHODS

A total of 48 femoral heads were obtained at operation from patients who had undergone endoprosthetic hip replacement. The specimens were subjected to manual rinsing or semiautomatic cleansing procedures with five different pulsatile lavage devices. After the cleansing procedures, polymethylmetacrylate bone cement was intruded into the cancellous bone under standardised conditions. Determination of cement penetration was done by computed tomography using an image processing software.

RESULTS

Irrespective of the nature of the lavage system tested, superficial cement penetration, both up to 2 mm and up to 3 mm, was significantly better after pulsatile high-pressure lavage than it was after manual rinsing of the specimens with a bladder syringe (P < 0.001 in each case). Whereas our experimental model did not show any significant differences between the lavage systems as regards the cementation results to a depth of up to 2 mm (P = 0.996), there were significant differences at a target depth of 3 mm (P < 0.05).

CONCLUSION

As compared with manual rinsing, pulsatile high-pressure lavage in vitro makes highly significant improvements in cement penetration into cancellous bone and should be regarded as an indispensable component of modern cementation techniques for endoprosthetic surgery. Up to the present we have not been able to ascertain what influence the different pulse characteristics of a pulsatile lavage system may have on the intended cementation result, whether it is impact force, pulse shape, pulse duration, flow rate or frequency. Appropriate investigations will be necessary.

The operation of the century: total hip replacement

In the 1960s, total hip replacement revolutionised management of elderly patients crippled with arthritis, with very good long-term results. Today, young patients present for hip-replacement surgery hoping to restore their quality of life, which typically includes physically demanding activities. Advances in bioengineering technology have driven development of hip prostheses. Both cemented and uncemented hips can provide durable fixation. Better materials and design have allowed use of large-bore bearings, which provide an increased range of motion with enhanced stability and very low wear. Minimally invasive surgery limits soft-tissue damage and facilitates accelerated discharge and rehabilitation. Short-term objectives must not compromise long-term performance. Computer-assisted surgery will contribute to reproducible and accurate placement of implants. Universal economic constraints in healthcare services dictate that further developments in total hip replacement will be governed by their cost-effectiveness.

Femoral cementing technique for hip resurfacing arthroplasty

The resurgence of metal-metal bearings has renewed interest in hip resurfacing, but a paucity of information exists regarding femoral cementing technique. We developed a laboratory model in which 72 open-cell foam specimens were used to simulate bone. Analyses of two cement viscosities, two foam porosities, and six cementing techniques were performed: manual cement application only, manual application and filling of one quarter of the component with cement, filling of half of the component, manual application and half component filling, full component filling, and manual application and full component filling. For manual application, cement was pressurized into the foam by rolling the finger tips. For component filling, a defined quantity of cement was poured into the component before pressing it onto the foam. Specimens were cut into quarters, and cement penetration was quantified in seven areas: top, chamfer, wall, interior area, and proximal, medial, and distal stem. The manual technique showed a 3-mm thick, even cement penetration of the outer fixation surface (top = 26 +/- 0 mm(2), chamfer = 14.9 +/- 0.2 mm(2), wall = 55.6 +/- 5.2 mm(2)). None of the other techniques showed a significantly higher penetration in these areas. Large differences were found between all techniques at the medial stem (27.7 +/- 17.5 mm(2), p < 0.001) and the interior area (128.5 +/- 69.6 mm(2), p = 0.013). An increasing degree of penetration occurred from manual cement application to manual application and full component filling. Sixteen specimens showed incomplete seating, which occurred with all techniques except the manual technique. The manual technique consistently gave an approximately 3-mm thick even cement penetration over the outer fixation area. Pouring any cement into the shell resulted in variable degrees of deeper penetration and a risk of incomplete seating, which have been associated with bone necrosis and early fracture.

Biomechanical evaluation of a new augmentation method for enhanced screw fixation in osteoporotic proximal femoral fractures

A biomechanical investigation on eight pairs of human cadaver proximal femurs was performed to evaluate the impact of a new augmentation method on the internal fixation of osteoporotic proximal femur fractures. The study focused on enhancing implant purchase to reduce the incidence of implant cut-out in osteoporotic bone. In a left-right comparison, a conventional hip screw fixation (control) was compared to the new cement augmentation method. After bone bed preparation through high pressure irrigation to remove fat, blood, and bone debris, the bones were augmented with low viscosity polymethylmethacrylate (PMMA) cement. Step-wise fatigue testing was performed by cyclically loading the femoral heads in a physiological manner, beginning at 1,500 N and increasing 500 N every 5,000 cycles to 4,000 N, and continuously monitoring head displacement. Failure was defined as >5.0 mm head displacement. The head displacement at 2,000 N was significantly smaller (p=0.018) for the augmented group as compared to the conventionally treated bones (0.09+/-0.01 mm vs. 0.90+/-0.32 mm; mean+/-SEM). The displacement rate at the second load step was significantly higher (p=0.018) for the conventionally treated bones as compared to the augmented ones. All of the nonaugmented specimens failed during testing, where 50% of the augmented specimens did not fail. The promising results of these experiments suggest that this new standardized irrigation/augmentation method enhances the implant anchorage and offers a potential solution to the problem of implant cut-out in osteoporotic metaphyseal bone.

[The influence of jet-lavage systems on in vitro cement penetration]

The benefit of pulsatile lavage on cement penetration in femoral cancellous bone is well known. The aim of this study was to determine the influence of different jet-lavage systems on cement penetration in a standardized cadaver study. Four different jet-lavage systems were compared (right vs left) in 30 paired human femora. After broaching, the femoral canal was lavaged with 1 l saline. The specimens were embedded in plastic pots, bone cement was applied in a retrograde manner and cement was pressurized using a standard pressure protocol with a constant force of 3,000 N. Horizontal sections were obtained at predefined levels using an automatic saw. Microradiographs were taken and analysed using image analysis to assess the extent of cement penetration. There were no significant differences in cement penetration into cancellous bone using the different jet-lavage systems. This technique is of great importance for obtaining a good interdigitation with cancellous bone. The different jet-lavage systems investigated in our study, however, seemed to be equally effective.

Factors affecting the cement penetration of a hip resurfacing implant: an in vitro study

An understanding of how the cementing technique influences cement penetration is important for surgeons to plan and conduct hip resurfacing procedures. Therefore the aim of this study is to determine the influence of the following parameters on cement penetration: use of pulse lavage, type of cement, and the standing period of the cement. Nine fresh frozen paired whole cadaver femora were used to investigate cement penetration. The femora were divided into three paired groups: (A) compared the use of pulse lavage to no pulse lavage, (B) compared two low viscosity bone cements SULCEM-3 (Zimmer GmbH, Switzerland) and Surgical Simplex (Stryker Orthopaedics, USA), and (C) compared bone cement viscosities using standing times of 1.5 min. and 3 min. The Durom Hip Resurfacing implant (Zimmer GmbH, Switzerland) was used in all groups. A single slice was taken out of the center of each head. Cement penetration ratio (penetration area divided by the bone area enclosed by implant) and mean cement penetration depth were measured. Cement penetration is increased using pulse lavage, and has the tendency to increase with increasing the cement standing time from 1.5 to 3 min. No difference in cement penetration was found when different cement brands of comparable viscosity were used.

CT analysis of defects of the cement mantle and alignment of the stem

Using a modern cementing technique, we implanted 22 stereolithographic polymeric replicas of the Charnley-Kerboul stem in 11 pairs of human cadaver femora. On one side, the replicas were cemented line-to-line with the largest broach. On the other, one-size undersized replicas were used (radial difference, 0.89 mm sd 0.13).

CT analysis showed that the line-to-line stems without distal centralisers were at least as well aligned and centered as undersized stems with a centraliser, but were surrounded by less cement and presented more areas of thin (< 2 mm) or deficient (< 1 mm) cement. These areas were located predominantly at the corners and in the middle and distal thirds of the stem. Nevertheless, in line-to-line stems, penetration of cement into cancellous bone resulted in a mean thickness of cement of 3.1 mm (sd 0.6) and only 6.2% of deficient and 26.4% of thin cement. In over 90% of these areas, the cement was directly supported by cortical bone or cortical bone with less than 1 mm of cancellous bone interposed.

When Charnley-Kerboul stems are cemented line-to-line, good clinical results are observed because cement-deficient areas are limited and are frequently supported by cortical bone.

Insertion of an expandable cement restrictor reduces intramedullary fat displacement

The insertion of an intramedullary cement restrictor can lead to the same pathophysiologic reactions that are well described as fat embolism syndrome after cement and stem implantation. Fat and marrow are forced into the draining veins of the femur. In this study, we compared the extrusion of intramedullary contents produced by the insertion of a commonly used gelatin (Biostop G/IMSET) and a new expandable cement restrictor (REX Cement Stop) in 7 paired, fresh-frozen femora. A further 9 pairs were used to evaluate the function of a custom-made application instrument, which allowed for suction during plug (Biostop G/IMSET) insertion. The oversized restrictor produced, on average, twice as much fat as the expandable restrictor (P = 0.0156). The gelatin plug with additional suction was not associated with reduced fat extrusion, because the suction device in its current design failed because of obstruction in most cases. The expandable restrictor showed favorable characteristics and has the potential to reduce the risk of fat embolism.

A new bleeding model of the human acetabulum and a pilot comparison of 2 different cement pressurizers

In this cadaver study, we compared 2 different acetabular cement pressurizers (Exeter and Bernoski type) in paired human acetabula with simulated intraosseous bleeding. Pressure transducers were used to record intra-acetabular pressures during pressurization. Anteroposterior radiographs of the entire specimens were taken. Subsequently, standardized 3-mm-thick sections were cut through the acetabula, which were then microradiographed to evaluate cement penetration. Adequate pressurization was obtained with either pressurizer. The peak and sustained pressures obtained with the Exeter pressurizer (peak, 80 kPa; sustained, 38 kPa) tended to be higher than the pressures obtained with the Bernoski pressurizer (73 kPa; 24 kPa; P > 0.05). Accordingly, a tendency toward improved cement penetration into cancellous bone was found using the Exeter pressurizer (P >.05).

Effect of bone porosity on the mechanical integrity of the bone-cement interface

BACKGROUND

Osteopenia is one factor that may influence the decision about the type of implant fixation to use in total hip arthroplasty. However, clinical studies generally do not associate the outcome of an arthroplasty with the degree of osteopenia. The mechanical integrity of the cement fixation of an implant may be affected by the relative degree of osteopenia, which could account for some of the variable long-term results after total hip arthroplasty performed with cement. The purpose of this study was to determine the effects of bone porosity, trabecular orientation, cement pressure, and cement penetration depth on fracture toughness at the bone-cement interface.

METHODS

Trabecular bone from the proximal part of bovine femora was used with a single brand of commercial acrylic bone cement to form compact-tension interface specimens representing a range of bone porosities, orientations, and cement pressures within a clinically achievable range. All specimens were loaded to failure with use of a servohydraulic testing machine, and fracture toughness at the interface was calculated. After testing, images of a representative sample of specimens were made with use of computed tomography to measure the penetration depth of the cement into the bone.

RESULTS

Significant correlations were found between fracture toughness and bone porosity, trabecular orientation, and cement pressure, with bone porosity having the strongest effect (p < 0.000015). Examination of the computed tomographic images also showed a significant correlation between fracture toughness and maximum cement penetration depth (p < 0.033), as well as significant partial correlations between maximum and mean penetration depth and bone porosity (p < 0.0037 and p < 0.0028).

CONCLUSION

The fracture resistance of the bone-cement interface is greatly improved when the ability of the cement to flow into the intertrabecular spaces is enhanced.

The measurement and comparison of jet characteristics of surgical pulse lavage devices

The characteristics of pulse waveform, pulse duration, pulse frequency, impact force/pressure, and flow rate of 4 commercially available pulse lavage devices are measured and compared. Validation of the measurements obtained is provided by a laboratory system that generates and measures precise jet waveforms. However, the value of the devices studied awaits clinical trials.