Aims

Total hip arthroplasty (THA) using the direct anterior approach (DAA) is undertaken with the patient in the supine position, creating an opportunity to replace both hips under one anaesthetic. Few studies have reported simultaneous bilateral DAA-THA. The aim of this study was to characterize a cohort of patients selected for this technique by a single, high-volume arthroplasty surgeon and to investigate their early postoperative clinical outcomes.

Aims

Cementless total knee arthroplasty (TKA) offers the potential for strong biological fixation compared with cemented TKA where fixation is achieved by the mechanical integration of the cement. Few mid-term results are available for newer cementless TKA designs, which have used additive manufacturing (3D printing). The aim of this study was to present mid-term clinical outcomes and implant survivorship of the cementless Stryker Triathlon Tritanium TKA.

Background

Direct anterior approach (DAA), total hip arthroplasty (THA, performed with the patient in the supine position, creates a unique opportunity to do bilateral THA under one anesthesia. Previous studies evaluating this option are limited by small sample size or lack of control group. The purpose of this study is to compare early clinical outcomes of simultaneous bilateral, unilateral and staged bilateral DAA-THA.

Introduction

Early ambulation after total hip arthroplasty (THA) predicts early discharge. Spinal anesthesia is preferred but can delay ambulation, especially with bupivacaine. Mepivacaine, an intermediate-acting local anesthetic, could enable earlier ambulation than bupivacaine. We hypothesized that patients who received mepivacaine would ambulate earlier than those who received hyperbaric bupivacaine or isobaric bupivacaine for primary THA.

Introduction

Cementless TKA offers the potential for strong fixation through biologic fixation technology as compared to cemented TKA where fixation is achieved through mechanical integration of the cement. Few mid-term results are available for newer cementless TKA designs that have used additive manufacturing (3-D printing) for component design. The purpose of this study is to present minimum 5-year clinical outcomes and implant survivorship of a specific cementless TKA using a novel 3-D printed tibial baseplate.

Aims

The aim of this study was to analyze the true costs associated with preoperative CT scans performed for robotic-assisted total knee arthroplasty (RATKA) planning and to determine the value of a formal radiologist’s report of these studies.

Introduction

Component position and overall limb alignment following total knee arthroplasty (TKA) have been shown to influence prosthetic survivorship and clinical outcomes¹. The objective of this study was to compare the accuracy to plan of three-dimensional modeled (3D) TKA with manual TKA for component alignment and position.

Introduction

Our purpose is to analyze the true costs associated with preoperative CT scans performed for robotic assisted TKA planning and also to determine the value of a formal radiologist reading of these studies.

Introduction

Opioid abuse is a national epidemic. Traditional pain management after total knee arthroplasty (TKA) relied heavily on opioids. The evidence that in-hospital multimodal pain management (MMPM) is more effective than opioid-only analgesia is overwhelming. There has been little focus on post-discharge pain management. The purpose of this study was to determine whether MMPM after TKA could reduce opioid consumption in the 30-day period after hospital discharge.

Introduction

Robotic-arm total knee arthroplasty (RTKA) was developed to potentially improve accuracy of bone cuts, component alignment, soft tissue balance, and patient outcomes. There is a paucity of data demonstrating that RTKA is superior to conventional total knee arthroplasty (CTKA) in terms of any of these metrics. This prospective comparative multicenter study was designed with these purposes in mind.

Background

Orthopedic surgeons have relied heavily on opiates after total hip replacement (THR) despite no clear evidence of benefit and a rapidly growing abuse epidemic. Multimodal analgesia may reduce or even obviate the need for opiates after elective surgery.

Dual mobility cups have two points of articulation, one between the shell and the polyethylene (external bearing) and one between the polyethylene and the femoral head (internal bearing). Movement occurs at the inner bearing; the outer bearing only moves at extremes of movement.

Dislocation after total hip arthroplasty (THA) is a cause of much morbidity and its treatment has significant cost implications. Dual mobility cups provide an increased range of movement and a may reduce the risk of dislocation.

This paper reviews the use of these cups in THA, particularly where stability is an issue. Dual mobility cups may be of benefit in primary THA in patients at a high risk of dislocation, such as those who are older with increased comorbidities and a higher American Association of Anesthesiology grade and those with a neuromuscular disease. They may be used at revision surgery where the risk of dislocation is high, such as in patients with many prior dislocations, or those with abductor deficiency. They may also be used in THA for displaced fractures of the femoral neck, which has a notoriously high rate of dislocation.

Cite this article: Bone Joint J 2016;98-B(1 Suppl A):60–3.

Previous clinical studies have documented the incidence of squeaking in subjects having a ceramic-onceramic (COC) THA. An in vivo sound sensor was recently developed used to capture sound at the THA interface. In this first study, it was determined that subjects having all bearing surface types demonstrated variable sounds. Therefore, in this follow-up study, the overall objective was to simultaneously capture in vivo sound and motion of the femoral head within the acetabular cup during weight-bearing activities for subjects implanted with one of four different ceramic-on-ceramic (COC) THA.

Twenty subjects, each implanted with one of four types of Ceramic-on-Ceramic THA (9 Smith and Nephew, 8 Stryker, 2 Wright Medical Technologies and 1 Encore) were analyzed under in vivo, weightbearing conditions using video fluoroscopy and a sound sensor while performing gait on a treadmill. Patients were pre-screened and two groups were defined: a group diagnosed as audible squeakers (9 THAs) and a control group of THA patients not experiencing audible sounds (11 THAs). Two tri-axial piezoelectric accelerometers were attached to the pelvis and the femoral bone prominences respectively. The sensors detect frequencies propagating through the hip joint interaction. Also, 3D kinematics of the hip joint was determined, with the help of a previously published 2D-to-3D registration technique. In vivo sound was then correlated to 3D in vivo kinematics to determine if positioning of the femoral head within the acetabular cup is an influencing factor.

For the audible group, two had a Smith and Nephew (S& N) THA, six a Stryker THA and one a Wright Medical (WMT) THA. Both of the S& N subjects, 5/6 Stryker and the Wright Medical subjects experienced femoral head separation. The maximum separation for those subjects was 4.6, 5.0 and 2.1 mm for the S& N, Stryker and WMT subjects, respectively. The average separation was 4.3, 2.0 and 2.1 mm for the S& N, Stryker and WMT subjects, respectively. For the eleven subjects in the control group, seven subjects had a S& N THA, two a Stryker and one each having a WMT and Encore THA. All 11 of these subjects demonstrated hip separation with the maximum values being 3.8, 3.4, 1.9 and 2.4 mm for the S& N, Stryker, WMT and Encore THA, respectively. The average separation values were 1.8, 2.3, 1.9 and 2.4 mm for the S& N, Stryker, WMT and Encore THA subjects, respectively.

Four distinct sounds were produced by subjects in this study, which were squeaking, knocking, clicking and grating. Only 3/20 subjects produced a “squeaking” sound that was detected using our sound sensor. One of these subjects had a Stryker THA and two had a WMT THA. Further analysis of the nine subjects who were categorized as audible squeakers revealed that only 0/2, 1/6 and 1/1 subjects having a S& N, Stryker and WMT THA, respectively, demonstrated a squeaking sound that was detected using our sound sensor. Both (2/2) S& N subjects demonstrated a knocking and clicking sound, but neither produced a grating sound, while 5/6 Stryker subjects produced a knocking sound, but only 1/6 demonstrated a clicking or grating sound. Besides the squeaking sound, the only other sound produced by the WMT audible squeaker was a knocking sound. Only 1/11 control group subjects demonstrated a squeaking sound, which was a subject having a WMT THA. With respect to the control group subjects having a S& N THA, 5/7, 1/7 and 3/7 subjects produced a knocking, clicking or grating sound, respectively. Only 1/2 subjects having a Stryker THA produced a knocking or grating sound.

This is the first study to compare multiple COC THAs in analyzing correlation of femoral head separation (sliding) and sound. It was seen that all the THA groups had occurrences of separation and each case of separation correlated with the sound data. These results lead the authors to believe that the influence of squeaking is multi-factorial, and not necessarily attributed only to the bearing surface material.

Squeaking in hip arthroplasty is now well-documented but hitherto poorly understood. In this paper, we report data progressively accumulated from a series of studies undertaken by our group to investigate the mechanisms of noise production associated with ceramic-on-ceramic bearings. We reviewed demographic and radiographic data comparing squeaking with silent hips. Edge loading of the acetabular components was investigated on retrieved bearings and with finite element analysis. The squeaking sound itself was further investigated through acoustic analysis. Squeaking occurs in younger, heavier, and taller patients.

We found a higher incidence of acetabular component malposition in squeaking hips and edge loading appears to be a causative factor. Finite element analysis revealed a stiffness mismatch between the shell and liner which may allow the shell to oscillate producing an audible squeak. Acoustic and modal analysis show that squeaking is due to a forced vibration and that the natural frequencies of the ceramic components are above the audible range, suggesting that resonance occurs in the metallic, not the ceramic parts. This phenomenon is related to patient factors, surgical factors, and implant factors, which may produce sound by a combination of edge loading of the ceramic and forced vibration of the acetabular shell and/or the femoral stem.

Purpose: Dislocation is one of the most common complications following total hip arthroplasty (THA), with rates reported between 1% and 3%, but as high as 6% using a posterior approach with metal on polyethylene bearing surfaces. The purpose of this study was to assess the dislocation rates in ceramic-on-ceramic THAs.

Method: Primary ceramic-on-ceramic (Stryker Orthopaedics) THAs performed at 9 institutions from October 1996 through July 2005 were included in the study (1635 hips in 1485 patients). Sixty-one percent were male. The average age was 52 years (range 15–83). Osteoarthritis was the leading reason for surgical intervention (86%). A posterior approach and 32 mm or 36 mm femoral head was used in the majority of patients (90%). Patients returned for routine clinical examination or were contacted by telephone to assess for dislocations at a minimum of one year (average three years) after surgery.

Results: Of the 1635 ceramic-on-ceramic THAs performed, there were 18 dislocations (1.1%). Of these, 15 were 32 mm femoral heads; 3 were 28 mm; none were 36 mm. The majority of dislocations occurred within 3 months after surgery (72%). Closed reduction was successful in 17 hips with one requiring a revision.

Conclusion: A low rate of dislocations in ceramic-on-ceramic THAs occurred in this study (1.1%). Compared with reported metal-on-polyethylene bearing surfaces, the ceramic-on-ceramic articulation design appears to have fewer dislocations. Other factors associated with this low dislocation rate may be decreased femoral neck diameters and/or larger average femoral head size in patients receiving the ceramic-on-ceramic design. These results will need to be compared with contemporary THA using different articular surfaces.

Squeaking in ceramic on ceramic bearing total hip arthroplasty is well documented but its aetiology is poorly understood. In this study we have undertaken an acoustic analysis of the squeaking sound recorded from 31 ceramic on ceramic bearing hips. The frequencies of these sounds were compared with in vitro acoustic analysis of the component parts of the total hip implant. Analysis of the sounds produced by squeaking hip replacements and comparison of the frequencies of these sounds with the natural frequency of the component parts of the hip replacements indicates that the squeaking sound is due to a friction driven forced vibration resulting in resonance of one or both of the metal components of the implant. Finite element analysis of edge loading of the prostheses shows that there is a stiffness incompatibility between the acetabular shell and the liner.

The shell tends to deform, uncoupling the shell-liner taper system. As a result the liner tends to tilt out of the acetabular shell and slide against the acetabular shell adjacent to the applied load. The amount of sliding varied from 4–40μm. In vitro acoustic and finite element analysis of the component parts of a total hip replacement compared with in vivo acoustic analysis of squeaking hips indicate that either the acetabular shell or the femoral stem can act as an “oscillator’ in a forced vibration system and thus emit a squeak.

Introduction: Squeaking has long been recognized as a complication in hip arthroplasty. It was first reported in the Judet acrylic hemiarthroplasty.¹ It was the squeak of a Judet prosthesis that led John Charnley to investigate friction and lubrication of normal and artificial joints which ultimately led to the concept of low friction arthroplasty. Ceramic on ceramic bearings were pioneered by Boutin in France during the 1970’s, but experienced unacceptably high fracture rates. Charnley demonstrated in vitro squeaking when he tested one of Boutin’s ceramic-on-ceramic bearings in his pendulum friction comparator.² Squeaking has also been reported in other hard on hard bearings, and can also occur after polyethylene bearing surface failure resulting in articulation between metal on metal or ceramic on metal surfaces.^3–6 Recently, squeaking has been increasingly reported in modern ceramic-on-ceramic bearings in hip arthroplasty. However, although well-documented, the aetiology of squeaking in ceramic on ceramic bearings is still poorly understood. The incidence ranges from under 1% to 10%.^7–10 It has been reported in mismatched ceramic couples,11and after ceramic liner fracture.^12,13 An increased risk of squeaking has been demonstrated with acetabular component malposition, as well as in younger, heavier and taller patients.⁹ However, it may also occur in properly matched ceramic bearings with ideal acetabular component position and in the absence of neck to rim impingement.^7–9 In rare cases, the squeak is not tolerated by the patient and has prompted a revision.

Under ideal conditions hard-on-hard bearings are assumed to be operating under conditions of fluid film lubrication with very low friction.^14,15 However, if fluid film lubrication breaks down leading to dry sliding contact there will be a dramatic increase in friction. If this increased friction provides more energy to the system than it can dissipate, instabilities may develop in the form of friction induced vibrations and sound radiation¹⁶. Friction induced vibrations are a special case of forced vibration, where the frequency of the resulting vibration is determined by the natural frequency of the component parts. Running a moistened finger around the rim of a wine glass is an example of this. [Appendix].

The hypothesis of this study is that the squeaking sound that occurs in ceramic on ceramic hip replacement is the result of a forced vibration. This forced vibration can be broken down into a driving force and a resultant dynamic response¹⁷. The driving force is a frictional driving force and occurs when there is a loss of fluid film lubrication resulting in a high friction force^14,15,18. The dynamic response is a vibration of a part of the device (the oscillator) at a frequency that is influenced by the natural frequency of the part¹⁶. By analyzing the frequencies of the sound produced by squeaking hip replacements and comparing them to the natural frequency of the component parts of a hip replacement this study aims to determine which part produces the sound.

Materials and methods: In vitro determination of the natural frequencies of implant components Modal analysis has suggested that resonance of the ceramic components would occur only at frequencies above the human audible range and that resonance of the metal parts would occur at frequencies within the human audible range. Furthermore, that resonance of the combined ceramic insert and titanium shell would not be within the human audible range. To test this hypothesis we performed a simple acoustic analysis. The natural frequency of hip replacement components was determined experimentally using an impulse-excitation method (Grindo-sonic). Components were placed on a soft foam mat in a quiet environment and struck with a wooden mallet. The sound emitted from the component was recorded on a personal computer with an external microphone with a frequency response which ranges from 50Hz to 18,000Hz (Beyerdynamic MCE87, Heilbronn, Ger-many). The computer has an integrated sound card with a frequency response from 20Hz to 24kHz (SoundMAX integrated digital audio chip, Analogue Devices Inc, Norwood, M.A.) and we used a codec with a frequency response from 20Hz to 20kHz (Audio Codec ’97, Intel, Santa Clara, CA). Sound files were captured as 16 bit mono files at a sample rate of 48000Hz using acoustic analysis software (Adobe Audition 1.5, Adobe Systems Incorporated, San Jose, California, USA). We performed fast Fourier transform (FFT) of the sound using FFT size 1024 with a Blackmann-Harris window to detect the frequency components of the emitted sound. (Fast Fourier transform is an accepted and efficient algorithm which enables construction of a frequency spectrum of digitized sound).

We tested the following components: modular ceramic/titanium acetabular components, which included testing the titanium shell and the respective ceramic inserts both assembled according to the manufacturer’s instructions and unassembled; titanium femoral stems and ceramic femoral heads both assembled and unassembled. A range of sizes of each component was tested according to availability from our retrieval collection.

In vivo acoustic analysis: Sound recordings were collected from 31 patients. Nineteen recordings were made at our institution: 16 of these were video and audio recordings and 3 were audio only recordings. Video recording was with a digital video camera recorder (Sony DCR-DVD101E Sony Electronics, San Diego, CA, USA) with the same external microphone used in the in vitro analysis. For 3 patients who could not reproduce the sound in the office we lent them a digital sound recorder for them to take home and record the sound when it occurred (Sony ICD-MX20, Sony Electronics, San Diego, CA, USA). This device has a In vivo acoustic frequency range from 60Hz to 13,500Hz. The remainder of the recordings were video and audio recordings made by surgeons at three other institutions on digital video camera recorders.

Sound files were captured and analyzed by the same method used in the in vitro analysis. Each recording was previewed in the spectral view mode which allows easy visual identification of the squeak in the sound recording. In addition all sound recordings were played, listening for the squeak. Once a squeak was identified a fast Fourier transform (FFT) was performed. We used FFT size 1024 with a Blackmann-Harris window which allowed us to easily pick out the major frequency components. All prominent frequency components were recorded at the beginning of the squeak and at several time points during the squeak if there was any change. A range was recorded for the fundamental frequency component. We were able to determine the frequency range of the recording device used by observing the frequency range of the background noise on the recording. We found that if a squeak was audible on the recording we had no difficulty determining its frequency regardless of the quality of the device used to make the recording or the amount of background noise.

The mean age of the patients was 54 years (23 to 79 years), mean height was 171cm (152 to 186cm) and mean weight was 79kg (52 to 111kg). There were 17 female and 14 male patients. There were nineteen ABGII stem and ABGII cup combinations, 10 accolade stem and trident cup, 1 Exeter stem and trident cup and 1 Osteonics Securfit stem with an Osteonics cup. Ethics committee approval was obtained for this project from our institution and from the referring institutions and informed consent was gained from the patients.

Finite element analysis of edge loading: Edge-loading wear which may provide a mechanism for failure of fluid film lubrication and may therefore play a role in squeaking. To evaluate edge loading further we conducted finite-element analysis (FEA).⁹ Computed tomography (CT) scans of an intact pelvis were obtained from visual human data set (VHD, NLM, Bethesda, Maryland). Slices were taken at 1mm thick with no inter-slice distance through the entire pelvis. The CT files were then read into a contour extraction program and saved into an IGES file format which was imported into PATRAN (MSC Software, Los Angeles, CA) to develop the pelvic geometry. The pelvis was meshed with 10 noded modified tetrahedral elements. The model was reconstructed with a 54mm titanium alloy generic acetabular shell and a 28mm alumina ceramic liner. The acetabular shell and ceramic liner were meshed using 8 noded hexahedral elements. The shell-liner modular taper junction incorporated an 18° angle. The implant contact conditions (Lagrangian multiplier) allowed the liner and shell to slide with a friction coefficient of 0.9. Tied contact conditions were applied between the generic acetabular shell and the bone representing bone ongrowth. Bone material properties were extracted from the CT files by taking the Hounsfield value and the coordinates and mapping to the element in the model allowing us to calculate the Young’s modulus for each element ¹⁹. Material properties for the shell and liner were based on published values²⁰ for titanium alloy and alumina ceramic