Introduction

The direct anterior approach (DAA) and the posterior approach (PA) are 2 common total hip arthroplasty (THA) exposures. This prospective study quantitatively compared changes in periarticular muscle volume after DAA and PA THA.

Background

The purpose of this study was to evaluate the clinical and radiographic outcomes of the rotating-platform, posterior-stabilized PFC Sigma at fifteen-year follow-up.

Background

Instability is one of the most common complications after total hip arthroplasty (THA), particularly when using the posterior approach. Repair of the posterior capsule has proven to significantly decrease the incidence of posterior hip dislocation. The purpose of the present study is to evaluate if braided polyblend suture provides a stronger repair of the posterior soft tissues when compared to a non-absorbable suture repair after a posterior approach to the hip.

Introduction

Anterior cruciate ligament (ACL) and multiligament knee (MLK) injuries increase the risk of development of knee osteoarthritis and eventual need for total knee arthroplasty (TKA). There is limited data regarding implant use and outcomes in these patients. The aim of this study was to compare the use of constrained implants and outcomes among patients undergoing TKA with a history of prior knee ligament reconstruction (PKLR) to a matched cohort of patients undergoing TKA with no history of PKLR.

Introduction

Potential implant and technique related factors to improve patellofemoral (PF) kinematics in total knee arthroplasty (TKA) are design of trochlear geometry and patella, restoration of posterior offset, patellar tilt and avoid overstuffing. The primary aim of this prospective, matched pair study was to assess the radiographic features of PF kinematics with an anatomic patella.

Introduction

Total hip arthroplasty (THR) with non-cemented or hybrid fixation remains one of the most successful procedures performed today. The aim of this study was to assess the safety and efficacy of a hydroxyapatite (HA) coated, hemispherical cup.

Background

Highly cross-linked polyethylene (HCLPE) was introduced to reduce wear and osteolysis in total hip arthroplasty (THA). There is no reported data regarding wear rates and clinical performance of Crossfire HCLPE (Stryker, Mahwah, New Jersey) in young and active patients. The purpose of this prospective study is to assess minimum 10-year wear rates and survivorship of Crossfire in young and active patients.

Introduction: In 1979, our senior author described his technique for correcting a flexion contracture during total knee arthroplasty (TKA) by additional resection of the distal femur and posterior capsular release; he also described his method of correction of a varus deformity by raising a subperiosteal sleeve from the proximal tibia. Due to concerns related to elevation of the joint line as well as flexion/extension gap asymmetry and instability, our technique has evolved into a methodical soft tissue release at the level of the joint line. Our hypothesis is that this technique effectively corrects both deformities, while reducing the complications related to the more traditional techniques.

The purpose of this study is to describe this technique and assess its effectiveness in a series of 31 consecutive patients.

Technique: Highlights of this technique are as follows:

This method involves osseous resections of 10mm from the level of the uninvolved surfaces of the femur and tibia in order to restore the mechanical axis.

Results: Over a 12 month span, we have corrected these biplanar deformities in 31 knees without residual instability. There were no residual flexion contractures greater than 5 degrees. The maximum varus corrected was 30 degrees, and the maximum flexion contracture corrected was 20 degrees. The mean coronal plane correction was to 5.5 degrees of valgus (range: 1 to 9 degrees).

Discussion: In a series of 31 consecutive patients, this technique was effective in correcting both deformities. We achieved a mean range of motion of 115 degrees, while avoiding elevation of the joint line or instability. Theoretically, this method should result in more optimal knee mechanics than traditional methods. While we are reporting good early results, a prospective, randomized controlled study is needed to better evaluate this technique.

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

Intro: There are few modern reports which document the results of all-polyethylene tibial components in younger, more active patients. The potential benefits of this design are the elimination of backside wear and lower implant cost than modular, metal-backed components.

From January 1992 to the present, 56 TKRs were implanted in 41 patients less than 60 years of age at the time of index surgery using a cemented all-poly tibial component with a PS design. Indications included all patients with osteoarthritis or post-traumatic arthritis without significant tibial bone loss. All patientswere followed prospectively with clinical and radiographic criteria asdefined by the Knee Society. Patient Assessment Questionnaires were used to quantify patient satisfaction, pain, and activity levels.

From January 1992 to the present, 56 TKRs were implanted in 41 patients less than 60 years of age at the time of index surgery using a cemented all-poly tibial component with a PS design. Indications included all patients with osteoarthritis or post-traumatic arthritis without significant tibial bone loss. All patientswere followed prospectively with clinical and radiographic criteria asdefined by the Knee Society. Patient Assessment Questionnaires were used to quantify patient satisfaction, pain, and activity levels.

Discussion: Since the mid 1980s, modular, metal-backed tibial trays have dominated the TKR market based on finite-element analysis studies which demonstrated superior force distribution compared to conventional all-poly components. As a result, backside wear has become an emerging problem and refocused design efforts on unitized components. Our clinical experience indicates an all-poly tibial component fixed with cement provides excellent performance and survivorship even in younger, more active patients.