The clinical results and basic science of total hip arthroplasty with porous-coated prostheses

Long-term survival and complication rate of cementless prosthetic stems in primary total hip arthroplasty categorized by types according to Mont classification: a regional registry-based study on 53,626 implants

INTRODUCTION

The purpose of this retrospective registry-based study is to assess survival and causes of failure of cementless stem implants used in total hip arthroplasty (THAs), to ascertain if there are differences when these are categorized according to the six types described by Mont.

METHODS

Data collected from the regional registry regarding all primary THAs performed from 2000 to 2019 were analyzed. Femoral prosthetic stems were divided into the six types of Mont classification. For each stem type, number of implants, survival and causes of failure were evaluated and compared.

RESULTS

The most frequently implanted stem type was the 3c type (53.4%). Type 1 had the lowest stem failure rate (1.6%), and type 6 showed the highest (3.9%). Periprosthetic fracture was the most frequent complication in type 6, accounting for 34.5% of failures. Aseptic loosening was the main complication in type 2 stems, accounting for 36.4% of failures. Pairwise comparisons showed significant higher survival of type 1 compared to type 3c (p = 0.000026) and type 6 (p = 0.000076), and between type 3a compared to type 3c (p = 0.03) and type 6 (p = 0.026).

CONCLUSION

Significant variations in implant survival rates were found among the six Mont-types of cementless stems. These findings emphasize the paramount importance of stem design and fixation area in determining long-term survival, providing a guidance for orthopedic surgeons in the selection of the most appropriate stem for primary THA, contributing to our understanding of cementless stem performance, presenting invaluable insights to further improve patient outcomes in THA surgery.

The torsion of the proximal femur in cementless total hip arthroplasty: a 3-dimensional evaluation

INTRODUCTION

The anatomy of the proximal femur at the time of total hip arthroplasty has been widely studied but the horizontal plane was never considered, or only limited to the torsion of the femoral neck.

METHODS

Using CT-scan images from a group of 178 patients scheduled for cementless total hip arthroplasty (THA), we analysed the evolution of the torsion of the proximal femoral metaphysis, in reference to the posterior bicondylar plane of the femur. The evolution of the torsion, between 20 mm below the centre of the lesser trochanter and 20 mm above, was evaluated.

RESULTS

In cases of primary osteoarthritis, osteonecrosis, rheumatoid arthritis and epiphysiolysis capitis femoris, the mean torsion decreased from 46° to 20° without significant differences in average values between the different diagnoses, but important individual variations were found. In the groups of dysplasia and congenital hip dislocation, the torsion values were significantly higher, decreasing in mean from 59° to 25° and 63° to 34° respectively, and with important individual variations.

CONCLUSIONS

These data are important when using cementless femoral stems, since an ideal fit-and-fill in the proximal femur zone has been shown to positively influence bone ingrowth of the stem. However, a strict adaptation of the stem to the medullary canal, without considering its torsion, can lead to an increased or decreased torsion of the prosthesis neck and thus to an instability of the arthroplasty. For these reasons, if a perfect adaptation of the stem to the intramedullary anatomy and an optimal reconstruction of the extramedullary anatomy are to be achieved, 3-dimensional planning should ideally be obtained for every patient. This will allow the best stem choice adapted to every single patient and every kind of anatomy.

[Research progress of cementless intercalary prosthesis stem]

OBJECTIVE

To review the research progress of cementless intercalary prosthesis stem.

METHODS

The literature about the cementless intercalary prosthesis in treatment of bone defects of extremities was reviewed, and the designing and application of prosthesis stem were analyzed.

RESULTS

Cementless intercalary prosthesis has the advantages of good biocompatibility. However, there are also some disadvantages, including the multiple factors affecting the fixation of the prosthesis stem and individual differences in the stability of the prosthesis. The methods to improve the fixation stability of prosthesis stem mainly include the optimization of prosthesis stem shape, addition of auxiliary fixation, and improvement of coating materials on the stem surface as well as porous structure of the stem surface. Among these methods, augment with auxiliary fixation has the most satisfactory effect on improving the stability of prosthesis. However, the deficiency of the method is the increasing risk of the larger incision exposure and surgical trauma.

CONCLUSION

Improving the design and fixation method of the cementless intercalary prosthesis stem can further improve the stability of the prosthesis. Under the premise of avoiding increasing surgical trauma as much as possible, addition of the auxiliary fixation can be a feasible choice to improve the fixation stability of prosthesis.

Finite-Element analysis of a lateral femoro-tibial impact on the total knee arthroplasty

BACKGROUND AND OBJECTIVE

Total knee arthroplasty (TKA) is a routine surgery performed to treat patients with severe knee osteoarthritis. The success of a TKA depends strongly on the initial stability of the prosthetic components and its long-term osseointegration due to the optimal distribution of mechanical stresses in the surrounding bones under the effect of the different biomechanical loads applied to the Femur-TKA-Tibia system. The purpose of this study is to analyze the level and the distribution of the induced stresses in a Femur-TKA-Tibia system subjected to combined triaxial forces, which mimic a femoral mechanical shock.

METHODS

In this study, complex TKA system implanted in both femoral and tibial bones has been analyzed numerically with a three-dimensional finite-element method. A virtual model is designed to examine in silico the effect of the combined triaxial forces acting on this prosthesis in femoral region. Anatomical three-dimensional finite-element models of both femoral and tibial bones were constructed to calculate the interfacial stresses around the TKA components. The 3D finite-element processing program ABAQUS was used to perform the analysis.

RESULTS

The stresses propagated in the bone regions adjacent to the TKA osseointegrated components, and the decreased in their magnitude to the outer region. These stresses reached the highest level in the cortical bone areas that are right next to the proximal upper attachment portions of the TKA osseointegrated components. The magnitude of the stresses in the tibial component is higher than that in the femoral component. Finally, it is very important to emphasize the role of the polyethylene articulating spacer in the shock absorption of bone support sections. Thus, this component should be preserved mechanically from the impact of high shocks in order to maintain healthy TKA systems.

CONCLUSIONS

Optimizing TKA model by controlling the biomechanical stresses distributed within its both components and supporting bones is a valid approach to achieving favorable long-term outcomes. The 3D finite-element analysis provides an effective pre-operative method for planning patient-specific TKA prostheses, and for designing future models that preserves the biomechanical function of the Femur-TKA-Tibia system.

Screw-hole clusters in acetabular cups: a morphological study of optimal positioning of screw-holes

BACKGROUND

Rigid and safe transacetabular screw fixation in total hip arthroplasty (THA) is achieved by pursuing deeper bone stock and avoiding injuries to the neurovascular structures, but these efforts can be restricted by the distribution of screw-holes on cups by the manufacturer. We therefore tried to determine: (i) optimal screw-hole positions on cups to allow anatomical placement of screws; (ii) rationality of the basic 3-screw-hole cluster on commercial cups; and (iii) the optimum method for placing commercial cups in accordance with acetabular anatomy.

METHODS

Periacetabular osseous structure of 64 hips and arterial structures of 50 hips were three-dimensionally reconstructed. Simulated transacetabular screw fixation during THA was performed in these hips with 3 different screw lengths (15, 25, and 35 mm) to define deeper and safer screw trajectories. Screw-hole locations of 7 commercially available cups were measured and matched with the periacetabular anatomy.

RESULTS

When the cup was placed into the acetabulum at 45° of abduction and 20° of anteversion, the optimal locations of 2 screw-holes on the cups were at 30° and 64° of latitude, with a 35° separation angle. The inversetriangle distribution pattern was safer than the triangle pattern in basic 3-screw-hole-cluster cups. When placing the commercial cups, 5°-10° of anterior rotation can be added to allow better screw trajectories.

CONCLUSIONS

Our study determined optimal screw-hole positions and their distribution pattern on cups. We describe methods to place the commercial cups that are not designed according to acetabular anatomy.

Cementless hip implants: an expanding choice

INTRODUCTION

Total hip replacement is a successful procedure with long survival records compared to other joint arthroplasties. Cemented implants have been available for many years, however the complications associated with loosening and, ultimately, failure over time has led to the development of cementless stems and implants.The ideal prosthesis should recreate a biomechanically normal hip joint, allow pain-free function and last the patient's life span without requiring revision. Optimal results with uncemented femoral stems rely on obtaining initial stability, osseointegration, biological fixation, and uniform stress transfer to the proximal bone.There are a multitude of factors that can affect the integration, stability and fixation of these stems into bone, and understanding these factors is the key to choosing the appropriate implant for a specific femur.

METHODS

This article aims to discuss cementless prostheses based on evidence-based practice. Geometry, roughness, stem coating, technique and bone quality are among the factors discussed. This was achieved through a review of the current literature.

CONCLUSIONS

Uncemented femoral stems have shown good, long-term survivorship and functional outcome, with promising results in younger patients.Limitations in the current literature make it difficult to assess and compare different designs to determine optimal indications for each type.Biological fixation, in which the prosthesis is directly fixed to the bone, is the preferred fixation method.Future studies of cementless implants should consistently address patient age, activity level, bone type, and deformities so that more definitive conclusions can be drawn about when to use each design.

The Corail® stem for the treatment of displaced femoral neck fractures - a viable alternative

Cementless hemiarthroplasty in hip fracture surgery has been associated with poorer outcomes and more pain than cemented hemiarthroplasty. The aim was to investigate clinical and radiographic outcomes for a cementless tapered titanium fully hydroyxapatite-coated (Corail® System) stem in this consecutive cohort of hip fracture patients. We retrospectively evaluated the results of 68 consecutive elderly patients with displaced intracapsular hip fractures, treated with this implant. Mean clinical follow-up was 4.3 years (2-6 years). One-year mortality was 24%. 95% of patients had no/occasional/mild mid-thigh pain, with moderate pain in 5%. 39% achieved independent or walking-stick mobility. 36 patients had follow-up radiography. Osseointegration was noted in 34, with a mixed bony/fibrous in-growth in 2. One patient had revision for subsidence of an undersized implant, with no conversions to total hip arthroplasty. The Corail® stem can be used effectively for the treatment of femoral neck fractures in the elderly.

Comparison of the recurrence risk of parameniscal cysts between patients treated with arthroscopic excision and arthroscopic decompression techniques

PURPOSE

To compare the recurrence risk of parameniscal cysts between arthroscopic meniscectomy with open cystectomy (arthroscopic excision) and entirely arthroscopic techniques with intra-articular cyst decompression (arthroscopic decompression).

METHODS

A retrospective longitudinal study was conducted at a medical centre in Taiwan between 2002 and 2012. Patients with symptomatic parameniscal cysts undergoing either arthroscopic excision or arthroscopic decompression were included. Parameniscal cyst recurrence was evaluated every 3 months after surgery. The recurrence risk associated with treatment group, cyst volume, and meniscal tear circumference was investigated.

RESULTS

This study included 241 young to middle-aged men and women. Of these, 112 underwent arthroscopic excision and 129 underwent arthroscopic decompression. During an average 26-month follow-up period, the arthroscopic decompression group had a sixfold higher recurrence risk [prevalence: 4 and 21 %, respectively; hazard ratio, HR 6.0 (95 % confidence interval, CI 2.3-15.6); p < 0.001] than the arthroscopic excision group. Furthermore, meniscal tears >12 mm in circumference and a cyst volume >2.4 cm(3) conferred a fivefold higher recurrence risk than both lesions of smaller dimensions, both in the overall population and in the arthroscopic decompression group [HRs 5.3 (95 % CI 2.3-12.2) and 5.35 (95 % CI 2.2-13.3), respectively; p values <0.001 for both].

CONCLUSIONS

The suggestion of our study is that the recurrence of parameniscal cysts may be strongly related to large cystic lesions and large meniscal tears. Arthroscopic excision is preferable for treating parameniscal cysts, which are large cystic lesions with large meniscal tears, to reduce the recurrence risk.

LEVEL OF EVIDENCE

III.

Porous metals and alternate bearing surfaces in shoulder arthroplasty

Total shoulder arthroplasty (TSA) provides an effective solution for the treatment of glenohumeral arthritis. However, long-term outcomes have been limited by glenoid component aseptic loosening and polyethylene (PE) wear. Previous attempts to improve glenoid fixation with metal-backed glenoids resulted in inferior results. Newer component designs that contain porous metal allow for biological ingrowth of the prosthesis, potentially improving longevity and overall outcomes. Porous metal can also improve humeral component fixation, obviating the need for cement and simplifying revision surgery. Advances such as highly cross-linked polyethylene (HXLPE), vitamin E-doped HXLPE, and alternate bearing surfaces like ceramics and pyrolytic carbon have proven to provide superior wear characteristics in other joint replacements and may prove beneficial in the shoulder as well.

Novel applications of osseointegration in orthopedic limb salvage surgery

Osseointegration is a biologic process vital to modern endoprosthetic fixation in orthopedic surgery. Numerous engineering advancements have improved the utilization of this technology in orthopedics; however, issues such as stress shielding, aseptic loosening, and bone loss remain an ongoing challenge. These host responses are especially problematic in limb salvage surgery. Novel applications of osseointegration have been developed to address some of these fixation issues with massive tumor endoprostheses. This articles reviews osseointegration and emerging novel applications of this technology in limb salvage surgery and future prosthetics for amputees.

Snapping knee caused by medial meniscal cyst

Snapping phenomenon around the medial aspect of the knee is rare. We present this case of snapping knee caused by the sartorius muscle over a large medial meniscal cyst in a 66-year-old female. Magnetic resonance images demonstrated a large medial meniscal cyst with a horizontal tear of the medial meniscus. Arthroscopic cyst decompression with limited meniscectomy resulted in the disappearance of snapping, and no recurrence of the cyst was observed during a 2-year follow-up period.

Pelvic Discontinuity Caused by Acetabular Overreaming during Primary Total Hip Arthroplasty

Intraoperative acetabular fracture is a rare complication of primary total hip arthroplasty (THA), typically occurring during impaction of the cementless acetabular component. Here we report an unusual case of pelvic discontinuity caused by overreaming of the acetabulum during primary THA. Restoration of posterior columnar continuity was achieved with an autologous fibular graft and a reconstruction plate. Wall defects and cavitary defects were reconstructed with metal mesh and femoral head allograft, followed by placement and fixation of a Kerboull-type acetabular reinforcement device. Previous reports of acetabular fracture during THA have indicated that it has a relatively good prognosis without extensive treatment. However, to our knowledge, there has been no report of pelvic discontinuity necessitating acetabular reconstruction surgery as an intraoperative complication of primary THA.

Cementless total hip arthroplasty using the Spongiosa-I fully coated cancellous metal surface: a minimum twenty-year follow-up

BACKGROUND

We present the results of cementless total hip arthroplasty performed with use of an anatomically adapted femoral stem and hemispherical cup with a fully coated Spongiosa-I metal surface, which was designed to achieve a surface similar to human cancellous bone. The purpose of the present retrospective case series was to determine the long-term outcomes of this hip arthroplasty system after a minimum of twenty years of follow-up.

METHODS

Between 1983 and 1985, 209 consecutive total hip arthroplasty procedures (199 patients) were performed with use of the first-generation Spongiosa metal-surface chromium-cobalt total hip implant with an articulating surface consisting of a ceramic head and an ultra-high-molecular-weight polyethylene liner. We report the clinical and radiographic outcomes, the rates of and reasons for revision, and the influence of sex and age on outcome and complications.

RESULTS

At the time of the latest follow-up, twenty-seven patients had died and thirteen patients had been lost to follow-up; none of these forty patients had had revision surgery. The outcomes for 159 patients (169 prostheses) were reviewed. The mean duration of follow-up was 262 months (range, 242 to 275 months). There were nineteen revisions, including fourteen revisions of the femoral stem, two revisions of the acetabular cup, and three revisions of both components. The mean Harris hip score for patients who did not undergo revision surgery was 82 points. The probability of survival of both components at twenty years, with revision for any reason as the end point, was 97%. The probability of survival of the acetabular component was 98%, and the probability of survival of the femoral component only was 86%. The probability of component survival was significantly increased among older patients.

CONCLUSIONS

The results of cementless hip arthroplasty with use of the first-generation Spongiosa implant were excellent at a minimum of twenty years of follow-up. The probability of survival of the acetabular component exceeded that of the femoral stem.

Cementless femoral fixation in total hip arthroplasty

A number of cementless femoral stems are associated with excellent long-term survivorship. Cementless designs differ from one another in terms of geometry and the means of obtaining initial fixation. Strict classification of stem designs is important in order to compare results among series. Loosening and thigh pain are less prevalent with modern stem designs. Stress-shielding is present in most cases, even with newer stem designs.

Pelvic Discontinuity Caused by Acetabular Overreaming during Primary Total Hip Arthroplasty

Intraoperative acetabular fracture is a rare complication of primary total hip arthroplasty (THA), typically occurring during impaction of the cementless acetabular component. Here we report an unusual case of pelvic discontinuity caused by overreaming of the acetabulum during primary THA. Restoration of posterior columnar continuity was achieved with an autologous fibular graft and a reconstruction plate. Wall defects and cavitary defects were reconstructed with metal mesh and femoral head allograft, followed by placement and fixation of a Kerboull-type acetabular reinforcement device. Previous reports of acetabular fracture during THA have indicated that it has a relatively good prognosis without extensive treatment. However, to our knowledge, there has been no report of pelvic discontinuity necessitating acetabular reconstruction surgery as an intraoperative complication of primary THA.

Acetabular Component Deformation under Rim Loading Using Digital Image Correlation and Finite Element Methods

Total hip replacement is a highly successful operation; restoring function and reducing pain in arthritis patients. In recent years, thinner resurfacing acetabular cups have been introduced in order to preserve bone stock and reduce the risk of dislocation. However concerns have been raised that deformation of these cups could adversely affect the lubrication regime of the bearing; leading to equatorial and edge contact, possibly causing the implants to jam. This study aims to assess the amount of deformation which occurs due to the tight peripheral fit experienced during press-fit by applying rim loading to three different designs of acetabular cup: a clinically successful cobalt chrome resurfacing cup, a prototype composite resurfacing cup and a clinically successful polyethylene monobloc cup. Digital Image Correlation (DIC) was used to measure the deformation and to validate Finite Element (FE) models. DIC provided a non-contacting method to measure displacement; meaning the load could be increased continuously rather than in steps as in previous studies. The physical testing showed that the cobalt chrome cups were significantly stiffer than the composite prototype and polyethylene cups. The FE models were in good agreement with the experimental results for all three cups and were able to predict the deformation to within 10%. FE models were also created to investigate the effect of cup outside diameter and wall thickness on stiffness under rim loading. Increasing outside diameter resulted in a linear reduction in stiffness for all three materials. Increasing the wall thickness resulted in an exponential increase in cup stiffness. Rim loading an acetabular shell does not accurately simulate the in vivo conditions; however it does provide a simple method for comparing cups made of different materials.

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.

Midterm survivorship of a press-fit, plasma-sprayed, tri-spike acetabular component

Press-fit acetabular cups without screw holes can limit migration of particulate wear debris and reduce risk of acetabular osteolysis and device loosening. The Tri-Spike cup (Biomet, Inc, Warsaw, Ind) includes a titanium alloy plasma spray porous surface and does not require screw fixation. We retrospectively examined the incidence of cup loosening and acetabular osteolysis after implantation of 45 cups (44 patients) with mean follow-up of 7.3 years (range, 4-9 years). Only one patient (one cup) had evidence of less than 1 mm of retroacetabular radiolucency at 3 years (nonprogressive), which was found to remain firmly fixed during revision of the aseptically loosened femoral component. No cups were removed or revised at latest follow-up. Projected Kaplan-Meier survivorship at 9 years was 100% for cup loosening/revision and 97.8% for radiolucency.

Effect of passivation and surface modification on the dissolution behavior and nano-surface characteristics of Ti-6Al-4V in Hank/EDTA solution

The aim of the present study was to investigate the effects of passivation treatment (34% nitric acid passivation, 400 ( composite function)C heated in air, and aged in 100 ( composite function)C de-ionized water) and surface modification (2 hr and 8 hr vacuum-brazed treatments) on the ion dissolution and nano-surface characteristics of Ti-6Al-4V exposed in Hank's solution with 8.0 mM ethylene diamine tetra-acetic acid (EDTA) at 37 ( composite function)C. The results indicated that the original nano-surface characteristics and microstructure would influence the ion dissolution but not change the capability of the Ca and P adsorption upon immersion. Of the three passivated treatments, 400 ( composite function)C thermal treatment for both 2 hr brazed Ti-6Al-4V (B2) and 8 hr brazed Ti-6Al-4V (B8) exhibits a substantial reduction in the constituent release compared to the acid passivated and water aged treatment, because the thicker thickness and rutile structure of surface oxide could provide the better dissolution resistance for 400 ( composite function)C-treated specimens. Moreover, the reduced Ti(2)Cu and increased alpha -titanium structure in B8 specimen could also improve ion dissolution resistance in comparison with B2 specimen. After soaking in Hank/EDTA solution, the adsorbed non-elemental Ca and P for all groups of specimens were observed by XPS analysis, and the AES depth-profile analysis indicate that the oxide films of all groups of specimens thicken with the longer immersion periods. The increasing oxide thickness may be the factor in the improved dissolution resistance at the longer immersion periods. The relation between lower dissolution rate and thicker oxide films were observed for all groups of specimens. The results suggest that the dissolution kinetics was governed by the metal ion transport through the oxide film in this study.

The relative cost of cemented and uncemented total hip arthroplasties

The use of uncemented femoral stems in primary total hip arthroplasty (THA) has been slow to develop in the UK because of the lack of encouraging published long-term follow-up data, the continued success of the cemented primary THA, and the perceived excessive relative cost of the uncemented THA. In this article, we argue that the total costs of 3 "proven" uncemented stems are comparable with commonly used cemented femoral components, when all necessary materials are taken into consideration. In addition, we will also discuss other potential benefits and drawbacks for considering the use of uncemented stems.

The design and production of Co–Cr alloy implants with controlled surface topography by CAD–CAM method and their effects on osseointegration

Improved fixation and increased longevity are still important performance criteria in the development of orthopaedic prostheses. The osseointegration of a series of implant designs made of conventional cobalt-chromium alloy was investigated, the shape of each implant being the critical variable. The shape was defined by computer-aided design with a view to maximising interdigitation of new bone with the implant. Two different process routes, conventional casting and selective laser sintering were employed, each process yielded implants that had identical surface topology but different microstructures. Hydroxyapatite (HA) was used to coat some samples by plasma spraying. Bone formation associated with each implant design was delineated through the administration of fluorescent vital dyes at three time points following their implantation into New Zealand white rabbits. After one month, specimens were harvested, resin embedded, serial sectioned and examined under fluorescent light microscopy. The amount of bone growth was quantified using image analysis. Plasma spray HA-coated samples promoted better osteogenesis and integration than uncoated samples. The extent of bone growth associated with identically shaped specimens fabricated by the SLS route was markedly greater, attributed to the microstructure of these implants.

Computational bone remodelling simulations and comparisons with DEXA results

Femoral periprosthetic bone loss following total hip replacement is often associated with stress shielding. Extensive bone resorption may lead to implant or bone failure and complicate revision surgery. In this study, an existing strain-adaptive bone remodelling theory was modified and combined with anatomic three-dimensional finite element models to predict alterations in periprosthetic apparent density. The theory incorporated an equivalent strain stimulus and joint and muscle forces from 45% of the gait cycle. Remodelling was simulated for three femoral components with different design philosophies: cobalt-chrome alloy, two-thirds proximally coated; titanium alloy, one-third proximally coated; and a composite of cobalt-chrome surrounded by polyaryletherketone, fully coated. Theoretical bone density changes correlated significantly with clinical densitometry measurements (DEXA) after 2 years across the Gruen zones (R2>0.67, p<0.02), with average differences of less than 5.4%. The results suggest that a large proportion of adaptive bone remodelling changes seen clinically with these implants may be explained by a consistent theory incorporating a purely mechanical stimulus. This theory could be applied to pre-clinical testing of new implants, investigation of design modifications, and patient-specific implant selection.

Fixation using acetabular reconstruction cage and cancellous allografts for intraoperative acetabular fractures associated with cementless acetabular component insertion

Displaced acetabular fractures that occur during insertion of cementless acetabular component are a rare but very serious complication. We report two cases that were treated successfully with the utilization of an acetabular reconstruction cage and morsellized allografts.

The role of titanium in the altered endotoxin-induced nitric oxide synthase expression in alveolar macrophages from titanium-alloy-implanted rats

We have found that the concentration of titanium (Ti) in the blood of patients with loosened Ti-alloy prostheses is elevated. An increase in the levels of elemental Ti in the blood and lung tissues of rats with an alloyed-Ti implant also has been found. The cellular reaction to elevated elemental Ti in the circulation remains unclear. We further performed experiments to examine the changes of inducible nitric oxide synthase (iNOS) expression in alveolar macrophages from alloyed-Ti-implanted rats. The elevation of nitrite and iNOS expression induced by lipopolysaccharide (LPS) was suppressed. The in vitro effect of a soluble form of Ti was further investigated. Ti (0.01-0.06 mM) inhibited the LPS-induced nitrite production and iNOS expression in alveolar macrophages from normal rats without any cytotoxic effects. LPS induced protein tyrosine phosphorylation, tyrosine-phosphorylation of lyn (a CD14-receptor-associated-tyrosine kinase), and degradation of IkappaB-alpha protein (inhibitor of NF-kappaB) in alveolar macrophages. These events were inhibited by co-incubation with Ti. These results indicate that elemental Ti may impair iNOS expression in alveolar macrophages through the alteration of protein tyrosine phosphorylation and NF-kappaB activation. The inhibitory action of Ti on cellular responses of alveolar macrophages may be anti-inflammatory and thus may depress local defense mechanisms related to microbial killing.

The middle-aged patient with hip arthritis: the case for extensively coated stems

Younger patients with a long life expectancy and higher activity levels who require total hip arthroplasty present a unique challenge to the reconstructive surgeon. To improve the longevity of total hip arthroplasty, particularly in younger, more active patients, femoral components inserted without cement have been used in an attempt to create a more durable reconstruction. Extensively-coated implants are an attractive option because they are associated with excellent initial implant stability and contact a large area of strong cortical bone in the femoral diaphysis where bony ingrowth reliably occurs. In a cohort of 304 patients (348 hips) who were between 45 and 65 years at the time of surgery and who were followed up for a mean of 14.2 years, 99.4% of the femoral reconstructions were stable with no cases of late failure secondary to loosening and a 96% rate of good to excellent clinical results. Although stress shielding, thigh pain, and difficulty of removal have been cited as problems with the use of these devices, in the current authors' experience they have not proved to be clinically relevant issues that limit the successfulness of total hip arthroplasty in this patient population.

Primary total hip arthroplasty using a grit-blasted, press-fit femoral prosthesis.Long-term results with survivorship analysis

BACKGROUND

This report presents the initial experience with the use of a grit-blasted, press-fit femoral prosthesis.

METHODS

The first 300 consecutive primary total hip arthroplasty procedures using a collarless, three-dimensional tapered, straight, titanium alloy stem with a grit-blasted surface (performed in 299 patients) were evaluated with independent clinical and radiographic follow-up examinations up to sixteen years. Eight different types of acetabular components, including a cementless all-polyethylene socket in 80 percent of the cases, were used. Radiographic evaluation, performed by an independent observer using a zonal analysis method, included assessment of component migration, Enghs implant-bone femoral fixation score, implant-bone demarcations, and periprosthetic osteolysis. The average duration of long-term radiographic follow-up was 12.6 years (range; 10 to 16 years).

RESULTS

At last examination only five hips were lost to follow-up and 69 patients were deceased. The overall mechanical failure rate (i.e. unstable with or without revision) of the femoral component was 2 percent. The femoral revision rate was 7 percent (two hips for aseptic loosening, five hips for septic loosening, and twelve hips with osseointegrated stems for severe progressive femoral osteolysis) and the acetabular revision rate was 27 percent (revised for either socket migration or progressive peri-acetabular osteolysis or both). Survivorship, based on any revision (femoral or acetabular) was 89 percent at ten years and 62 percent at fourteen years; survivorship of the femoral component was 95 percent at ten years and 90 percent at fourteen years. The incidence of femoral periprosthetic osteolysis, by radiographic examination at ten years or more was 47 percent, including 12 hips (5 percent) with distal endosteal osteolysis. Femoral implant-bone fixation was stable, bone-ongrowth in 97 percent; stable, fibrous-fixation in 1 percent, and unstable, fibrous-fixation in 2 percent of the cases.

CONCLUSIONS

The grit-blasted, press-fit, collarless, tapered femoral component continued to per-form well clinically and radiographically up to sixteen years of follow-up despite the challenging environment of periprosthetic osteolysis associated with the acetabular component design. The high incidence of failure among the cementless all-polyethylene sockets was not unexpected and the use of this acetabular implant was discontinued in 1985. While considered a "first-generation" cementless stem, this implant is still in use virtually without design modifications. This study demonstrates the durability of the results of the grit-blasted femoral component and indicates that such an implant offers a viable alternative for fixation without bone cement. (Hip International 2002; 2: 55-72).

Second-generation cementless total hip arthroplasty. Eight to eleven-year results

BACKGROUND

Second-generation cementless femoral components were designed to provide more reliable ingrowth and to limit distal osteolysis by incorporating circumferential proximal ingrowth surfaces. We examined the eight to eleven-year results of total hip arthroplasty with a cementless, anatomically designed femoral component and a cementless hemispheric acetabular component.

METHODS

Ninety-two consecutive primary total hip arthroplasties with implantation of a femoral component with a circumferential proximal porous coating (Anatomic Hip) and a cementless hemispheric porous-coated acetabular component (Harris-Galante II) were performed in eighty-five patients. These patients were prospectively followed clinically and radiographically. Six patients (seven hips) died and five patients (seven hips) were lost to follow-up, leaving seventy-four patients (seventy-eight hips) who had been followed for a mean of ten years (range, eight to eleven years). The mean age at the time of the arthroplasty was fifty-two years.

RESULTS

The mean preoperative Harris hip score of 51 points improved to 94 points at the time of final follow-up; 86% of the hips had a good or excellent result. Thigh pain was reported as mild to severe after seven hip arthroplasties. No femoral component was revised for any reason, and none were loose radiographically at the time of the last follow-up. Two hips underwent acetabular revision (one because of dislocation and one because of loosening). Kaplan-Meier survivorship analysis was performed with revision or loosening of any component as the end point. The ten-year survival rate was 96.4% +/- 2.1% for the total hip prosthesis, 100% for the femoral component, and 96.4% +/- 2.1% for the acetabular component. Radiolucencies adjacent to the nonporous portion of the femoral component were seen in sixty-eight (93%) of the -seventy-three hips with complete radiographic follow-up. Femoral osteolysis proximal to the lesser trochanter was noted in four hips (5%). No osteolysis was identified distal to the lesser trochanter. Periacetabular osteolysis was identified in twelve hips (16%). Five patients underwent exchange of the acetabular liner because of polyethylene wear.

CONCLUSIONS

This second-generation cementless, anatomically designed femoral component provided excellent clinical and radiographic results with a 100% survival rate at ten years. The circumferential porous coating of this implant improved ingrowth and prevented distal osteolysis at a mean of ten years after the arthroplasty.

Inhibition of osteopenia by low magnitude, high-frequency mechanical stimuli

The identification of anabolic agents for the treatment of metabolic bone disease is a highly prized, and elusive, goal. In searching for the osteogenic (bone-producing) constituents within mechanical stimuli, it was determined that high frequency (10-100 Hz) and low magnitude (<10 microstrain) stimuli were capable of augmenting bone mass and morphology, thereby benefiting both bone quantity and quality. Using animal models, it is shown that these mechanical signals can double bone-formation rates, inhibit disuse osteoporosis and increase the strength of trabecular bone by 25%. Considering that the magnitude of these mechanical signals are several orders of magnitude below those which cause damage to the bone tissue, it is proposed that this modality could be useful in the treatment of metabolic bone diseases.

Arthroscopic treatment of lateral meniscal cysts using an outside-in technique

This paper describes 19 cases of lateral meniscal cysts treated arthroscopically using an outside-in technique. In all patients, a horizontal or radial lesion (or both) of the meniscus was present. After the meniscal lesion was arthroscopically removed, the cyst was decompressed both from inside and percutaneously from outside with a motorized instrument introduced through a transmeniscal approach. The follow-up ranged from 2 to 5 years with an average of 3.3 years. On the basis of the evaluation scale developed by Cerullo et al. (1991), the results were rated excellent or good in 17 patients and fair in 2. No patient had cyst recurrence. The computed tomography follow-up examination, done in 10 of the 19 patients after an average of 3 years, showed a good remodeling of the meniscus. One of the two patients with a fair result had hypermobility of the posterior horn of the lateral meniscus due to the resection of the meniscal tissue overlying the popliteus tendon, whereas the other had pain and patellar crepitation owing to a preexisting patellofemoral abnormality.

Clinical experience with a proximally porous-coated second-generation cementless total hip prosthesis: minimum 5-year follow-up

This study reports the minimum 5-year follow-up of our experience with the Porous-Coated Anatomic E (PCA-E) series femoral stem and the modular acetabular cup. A total of 115 consecutive total hip replacements using PCA-E series (Howmedica, Rutherford, NJ) were performed in 108 patients. Six patients whose hips were performing well clinically died before 5-year follow-up and were excluded from the final evaluation. The remaining 109 hips (102 patients) were assessed at a mean follow-up of 72 months (range, 60-84 months). The hip diagnoses were osteoarthritis in 73, osteonecrosis in 31, rheumatoid arthritis in 2, and hip dysplasia in 3. The mean age was 56 years (range, 24-83 years). Three hips were revised: 1 because of late hematogenous infection, 1 because of aseptic loosening of the femoral component, and 1 because of postoperative loosening of an acetabular component. The Harris hip scores improved from a mean of 50 points (range, 20-66 points) preoperatively to a mean of 92 points (range, 64-100 points) at final follow-up. The score differed in each Charnley functional class, with a mean of 93 points (range, 72-100 points) in 57 hips of class A (no other joint involvement); 90 points (range, 58-100 points) in 26 hips of class B (opposite hip involvement); and 85 points (range, 37-100 points) in 26 hips of class C (multiple joint involvement or severe systemic disease). Out of 106 hips that had a full radiographic evaluation performed, 103 femoral components revealed stable bony ingrowth, 2 revealed stable fibrous ingrowth, and 1 showed migration with progressive loosening. This patient with radiographic loosening has minimal symptoms and has not required or been offered further surgery (Harris hip score of 86 points). The low aseptic loosening rate (2%) at minimum 5-year follow-up compares favorably with any cemented or cementless series. The osteolysis that was seen was focal and localized. The short follow-up does not allow determination of progression. There were no cases of distal osteolysis. We attribute the improved results from reported first-generation experience to multiple factors, including increased number of sizes (9 vs 6), increased proportional metaphyseal size, improved polyethylene manufacture (ram extruded vs machined), improved acetabular locking mechanism, and change to 26-mm from 32-mm femoral heads.

Proximally porous-coated ingrowth prostheses: limits of use

Callaghan has suggested that the most important factor in obtaining optimal results after total hip arthroplasty may be the ability to determine when to use cemented or cementless fixation. This article has presented the indications and relative contraindications for use of proximally porous-coated prostheses. Midterm results suggest that with appropriate patient selection, excellent clinical results can be achieved with currently available proximally porous-coated prostheses. Use of proximally coated prostheses is indicated for primary total hip arthroplasty in patients aged >70 years with good bone stock. Relative contraindications are based on interference with bone ingrowth or with the ability to achieve a congruent fit, both of which preclude establishment of rigid initial stability. These conditions include metabolic bone disease such as osteoporosis, osteomalacia, Gaucher's disease, sickle cell disorders, and Paget's disease; significant anatomical distortion, as seen in developmental dysplasia of the hip with anteversion, prior osteotomy, or intertrochanteric fracture; Dorr type C bone; and current treatment with radiation, chemotherapy, indomethacin, or diphosphonates. The same relative contraindications to use are applicable in revision situations. Further, proximally porous-coated prostheses should not be used for revision arthroplasty in the setting of massive bone loss, limited life expectancy, or inability to participate in protected weight bearing. These devices may be used successfully in revision arthroplasty when the hip has minimal or moderate bone loss, and occasionally in the setting of severe bone loss. As further information is revealed through the long-term (10-20 years) results of proximally coated prostheses, further refinements and knowledge of the indications and contraindications for the use of these prostheses will be revealed.

A randomized trial of hydroxyapatite coated prostheses in total hip arthroplasty

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

Acetabular fracture associated with cementless acetabular component insertion: a report of 13 cases

Acetabular fracture during insertion of a cementless acetabular component occurred in 13 patients. The preoperative diagnosis was osteoarthritis in 6 patients, rheumatoid arthritis in 2 patients, avascular necrosis in 3 patients, hip fracture nonunion in 1 patient, and developmental dysplasia of the hip in 1 patient. Several different components were used; however, the acetabulum was underreamed by 1 to 3 mm in all cases. The acetabular fracture was identified in 9 of 13 cases intraoperatively. The fracture was identified on postoperative radiographs for the other 4 cases. Fractures were treated by a variety of means, including the addition of augmentation screws in or around the cup, use of autograft bone at the fracture site, modified postoperative weight-bearing status, and immobilization. In 2 cases, the socket needed to be revised after it progressively migrated and failed. One patient had cup migration, and another had a radiolucent line about the cup but was not symptomatic enough to require revision. In 3 of these 4 cases, the fracture was not identified intraoperatively. Underreaming of the acetabulum and use of an oversized acetabular component has been recommended to improve the initial stability of the acetabular component during total hip arthroplasty. Impaction of an oversized component requires bone to undergo plastic deformation if the cup is to be fully seated. Theoretically, this technique provides improved component stability with enhanced osseous ingrowth into the cup. The 13 cases reported in this study demonstrate that acetabular fracture is a complication that may occur in association with uncemented hip arthroplasty, particularly if oversized components are used. The importance of recognizing acetabular fractures intraoperatively and the need to institute appropriate treatment to ensure a stable acetabular component is emphasized. In patients with osteoporotic bone, line-to-line reaming with use of a cementless acetabular component or insertion of a cemented socket may be considered to avoid this significant complication.

The effect of bone compaction on early fixation of porous-coated implants

The effect of a bone compaction technique versus conventional drilling on the early fixation of porous-coated implants was examined in a canine model. Compaction dilation resulted in a significant increase in implant fixation stiffness (P < .01) and ultimate fixation strength (P < .01) at 0 and 3 weeks. Fixation stiffness remained significantly increased at 6 weeks (P < .01); however, the ultimate fixation strength was not statistically significant between the 2 techniques (P > .05). There was no significant difference in either fixation value at 9 weeks (P > .05). Histological examination of the bone-implant interface demonstrated an increase in the density of cancellous bone immediately adjacent to the implants placed in the compaction dilated holes. The results of this study suggest that the compaction method of host bone preparation may optimize the initial stability of the implant interface of porous-coated prostheses.

Intermediate clinical follow-up of a dual-radius acetabular component

In this study, 92 primary total hip arthroplasties were performed in 83 patients using a porous-coated, dual-radius, cementless, acetabular component. All hips underwent line-to-line dome reaming with press-fit implantation that was judged to have complete bone contact. This acetabular shell provides a 1-mm oversized peripheral rim, which adds excellent initial stability while allowing complete bone contact in all hips. No fractures occurred. In 83% of hips, adjunctive screw fixation was not necessary. At a minimum of 4 years, follow-up, there were no revisions, no acetabular migration, one case of acetabular erosion consistent with osteolysis, and the average Harris Hip Score was 95. The design features of this new acetabular component have provided excellent fixation with complete initial bone contact, resulting in satisfactory intermediate clinical and radiographic results. The design provides excellent peripheral stability and complete bone contact.

Osseointegration of surface-blasted implants made of titanium alloy and cobalt-chromium alloy in a rabbit intramedullary model

The purpose of this study was to compare the osseointegration of surface-blasted Ti6A14V and CoCr implants in vivo. Ti6A14V and CoCr rods blasted with 710 microm A12O3 particles were bilaterally press-fit into the medullary space of distal femora of 24 rabbits. Evaluation was made radiographically, histologically, histomorphometrically (3, 6, and 12 weeks after implantation), and mechanically (12 weeks). Both Ti6A14V and CoCr implants demonstrated good biocompatibility radiographically and histologically. Toluidine blue-stained sections revealed an osteoconductive effect of the blasted surface, and fluorochrome labeling analysis showed active bone formation at the bone-implant interface at as late as 12 weeks for both specimens. CoCr showed significantly lower interfacial shear strength than Ti6A14V although the bone contact area with the implant surface was comparable and no intervening soft tissue at the bone-implant interface could be seen for either implant by scanning electron microscopy backscatter analysis. Unmineralized tissue (cartilage and osteoid) was observed more frequently on the CoCr surface than on the Ti6A14V surface. These data show less osseointegration of CoCr implants with this blasted surface for this short period, possibly due to a slight difference in surface roughness and some negative effects of CoCr on bone attachment.

Concentration of metal elements in the blood and urine in the patients with cementless total knee arthroplasty

Titanium (Ti), cobalt (Co) and chromium (Cr) element concentrations in the whole blood and urine specimen in 40 patients with cementless total knee arthroplasty were determined by the electrothermal atomic absorption spectrophotometry. Their ages ranged from 55 to 78 years (mean, 65 years). Twenty of them had loosening of prosthesis and underwent revision surgery, including 4 subjects with Ti-6Al-4V alloy prosthesis and 16 subjects with Co-Cr-Mo alloy prosthesis. The other 20 patients had well-functioning stable prosthesis, including 5 subjects with Ti-6Al-4V alloy prosthesis and 15 subjects with Co-Cr-Mo alloy prosthesis. The mean duration of prostheses implantation in patients with loosened or well-functioning prostheses were 6.5 and 4.0 years, respectively. The control group consisted of 20 age-matched normal subjects who did not undergo any metal implant surgery. Analysis of variance showed that the metal element concentrations in the whole blood, either Co, Cr or Ti, was statistically higher in the patients with loosened prosthesis than the other two groups. However, the metal element concentrations in the urine did not show any difference. The linear regression analysis showed a moderate positive relationship between the metal element concentrations, either Co or Cr elements, in whole blood and urine only in the patients with loosened prostheses. In conclusion, elevated concentration of metal elements may indicate a loosening of prosthesis while the clinical significance of the metal element concentration in the urine needs further investigation.

Arthopor 2 acetabular component with screw fixation in primary hip arthroplasty: a 7- to 9-year follow-up study

The first 100 consecutive primary hip arthroplasties with the Arthopor 2 acetabular component (Joint Medical Products, Stamford, CT) with supplemental screw fixation performed by the senior author were prospectively studied. The mean patient age was 57 years. Seventy-seven cemented and 23 cementless stems were placed, with 32-mm femoral heads used in most of the patients. Eighty-six hips were reviewed at 7-8.8 years (mean, 7.8 years). The mean Harris hip score at final follow-up evaluation was 94 points. No cups have been revised, although 2 cups in patients with radiation osteonecrosis were loose radiographically. One patient underwent revision of a severely worn liner. Despite a relatively high mean linear wear rate of 0.27 mm/y (range, 0.13-0.57 mm/y), no radiographic evidence of pelvic osteolysis was seen. The Arthopor 2 cup performed well with respect to pelvic osteolysis, despite the presence of substantial polyethylene debris. The relatively high polyethylene wear rate is attributed in part to the younger patient population and the use of 32-mm femoral heads paired with thin polyethylene liners.

Bipolar hemiarthroplasty for primary osteoarthritis of the hip: a review of 41 cases with 8 to 10 years of follow-up

This article reports the results of 41 hips in 36 patients who underwent bipolar hemiarthroplasty for primary osteoarthritis of the hip. Surgical technique included a complete capsulectomy and light reaming of the acetabulum in all patients. The average follow-up was 8.9 years with a minimum of 8 years. Harris hip scores improved from 49 preoperatively to 93 at the latest follow-up, with 95% of the hips rated as excellent or good. Two patients had mild, intermittent groin pain, while a third developed recalcitrant pain necessitating revision. Migration of the bipolar cup was minimal with an average of 2.3 mm superior and 2.1 mm medial migration. Survivorship analysis demonstrated an 89.5% survival rate at 10 years.

Immunohistochemical analysis of matrix proteolytic enzymes in the periprosthetic tissue in the patients with loosening prostheses

Regional periprosthetic bone resorption plays an important role of prosthesis loosening. In order to study the possible mechanisms of loosening, we investigated the presence of matrix proteolytic enzymes in the periprosthetic tissue by immunohistochemical technique in 72 patients undergoing revision operation of loosened joint prosthesis, including 22 males and 50 females and aged from 19 to 88 years (mean, 61.7 years). Thirty-nine patients had a loosened hip prosthesis (18 males and 21 females) whereas 33 patients had a loosened knee prosthesis (4 males and 29 females). Tissue specimens collected during revision surgery underwent thin slide sections and H & E staining, and were observed under light microscopy and polarized-light microscopy. The results showed many macrophages, histiocytes, fibroblasts, as well as many phagocytosed metal debris and polyethylene debris in the periprosthetic tissues, suggesting an active bone resorption. Furthermore, we used immunohistochemical techniques to detect the distribution of matrix proteolytic enzymes in periprosthetic tissue, including lysosome enzymes (cathepsin B, cathepsin D and cathepsin G), and matrix metalloproteinase (MMPs, MMP-1, MMP-2, MMP-3). The immunostaining were classified as strong positivity, > 70% positive cells; moderate positivity, 20-70% positive cells; weak/negative, < 20% positive cells. The results showed that cathepsin B, cathepsin D and cathepsin G were found in most fibroblasts and macrophage-like cells, including multinuclear giant cells and epithelioid cells. MMPs were found in most fibroblasts and macrophage-like cells, as well as a scant amount in the extracellular matrix. These enzymes were also found in or around blood vessels, the endothelial cells in the richly vascularized tissue. All negative controls showed no staining. The results of immunoreactive staining ranged from 61.1% to 68.1% of strong to moderate positivity. Since these enzymes were related to the degradation of matrix protein, they may be related to the periprosthetic bone resorption. The further clinical significance needs further investigation.

Sonographic appearances of meniscal cysts

PURPOSE

This study was conducted to define the sonographic appearances of cysts of the tibial menisci.

METHODS

Thirteen cases of meniscal cyst, proven by magnetic resonance imaging (MRI), were assessed using high-resolution sonography, and results of the 2 imaging modalities were correlated.

RESULTS

Seven meniscal cysts were lateral to the joint line, and 6 were located medially. MRI showed all 13 cysts to be associated with a tear of the adjoining meniscus. On sonograms, cyst size varied from 9 to 56 mm. Echotexture varied from uniformly hypoechoic or hypoechoic with echogenic septa to heterogeneously hyperechoic. Septated cysts were demonstrated by MRI and sonography.

CONCLUSIONS

Because of their diverse echo patterns, meniscal cysts may be easily mistaken for soft-tissue tumors, ganglions, or other lesions, which may result in surgery being inappropriately recommended. This is particularly true in the case of echogenic cysts. The cardinal sonographic characteristic of a meniscal cyst is its continuity with the meniscus, not its echotexture.

Scandinavian multicenter porous coated anatomic total hip arthroplasty study. Clinical and radiographic results with 7- to 10-year follow-up evaluation

Four hundred ninety-four patients (539 hips) with a mean age of 50.1 (SD, 9.7) years entered a prospective, multicenter study of the Porous Coated Anatomic (Howmedica, Rutherford, NJ) total hip arthroplasty. The preoperative diagnoses were primary osteoarthrosis (297 hips), secondary osteoarthrosis to childhood diseases (88 hips), fracture (73 hips), inflammatory arthritis (26 hips), idiopathic avascular necrosis (28), and miscellaneous (27 hips). After a mean follow-up period of 6 years and 10 months, 71 hips had been revised. The mean Harris hip score increased from 43 (15.7) to 94 (7.4) at the last follow-up evaluation, without any deterioration with time. After 7 years, the combined survival rate for the cup and/or stem using revision as endpoint was 92.2%. Radiographic failure, defined as migration of either component more than 5 min and/or focal osteolysis, was registered in 72 stems and 96 cups. The combined clinical (revision) and radiographic 7-year survival rates were 61.1 (+/-5.2) and 59.7 (+/-5.3) for the stem and cup, respectively. Statistical analysis revealed that young age and poor fill rate influenced the rate of stem failure, whereas cup failure was difficult to predict. Four variables were associated with stem subsidence: loosening of beads, pedestal formation, sclerotic lines in Gruen zone 7, and acetabular granuloma. According to our findings, the 5- to 10-year complication rate with this implant is high. Therefore, continuous radiographic follow-up evaluation of these cases is strongly recommended, to enable revision before severe destruction of bone or catastrophic clinical failure has occurred.

Differentiation of the bone-tissue remodeling response to axial and torsional loading in the turkey ulna

The ability of bone tissue to differentiate between axial and torsional loading was determined with use of a functionally isolated turkey-ulna model of bone adaptation. Surface modeling and intracortical remodeling were quantified after four weeks of 5000 cycles per day of axial loading sufficient to cause 1000 microstrain normal to the long axis of the bone (five ulnae), 5000 cycles per day of torsional loading sufficient to cause 1000 microstrain of shear strain (five ulnae), or disuse (six ulnae). Of these three distinct regimens, only disuse caused a significant change in gross areal properties (12 per cent loss of bone; p < 0.05) as compared with those in the contralateral, intact control ulnae (sixteen ulnae). This finding suggested that both axial and torsional loading conditions were suitable substitutes for functional signals normally responsible for bone homeostasis. However, the intracortical response was strongly dependent on the manner in which the bone was loaded. Axial loading increased the number of intracortical pores by a factor of seven as compared with that in the controls (246 +/- 40.5 compared with 36 +/- 8.5 pores); it also increased the area lost because of porosis as compared with that in the controls (1.39 +/- 0.252 compared with 0.202 +/- 0.062 square millimeter); however, the mean size of the individual pores was similar to that in the controls (0.00565 +/- 0.0019 compared with 0.00561 +/- 0.0029 square millimeter). Conversely, torsional loading failed to increase substantially the number of pores (67 +/- 22.6 pores), the area of bone lost because of porosis (0.352 +/- 0.114 square millimeter), or the size of the pores (0.00525 +/- 0.0035 square millimeter) as compared with those in the controls. Although disuse failed to increase substantially the number of intracortical pores (59 +/- 22.4 pores), significant area (1.05 +/- 0.35 square millimeters; p < 0.05) was lost within the cortex because of a threefold increase in the mean size of each pore (0.0178 +/- 0.0126 square millimeter). It appears that bone tissue can readily differentiate between distinct components of the strain environment, with strain per se necessary to retain coupled formation and resorption, shear strain achieving this goal by maintaining the status quo, and axial strain increasing intracortical turnover but retaining coupling. While it is clear that load influences bone mass and morphology, it is also clear that specific parameters within the strain environment have distinct strategic roles in defining this architecture.

Clinical and radiographic outcome of a cementless, titanium, plasma spray-coated total hip arthroplasty femoral component. Justification for continuance of use

Between 1984 and 1986, 177 nonconsecutive, primary total hip arthroplasties were performed in 150 patients using the Mallory-Head Porous femoral component (Biomet, Warsaw, IN) inserted without cement. Average time to follow-up evaluation for the entire population (including all early revisions) was 76 months (6.3 years). There were 10 revisions (6%) with an average time to revision of 50 months (4.2 years). Two revisions were for component undersizing; three revisions were for aseptic loosening; four revisions were for acetabular component failure and one revision was due to a femoral fracture secondary to trauma. At the most recent follow-up visit, the average Harris hip score for all hips increased from 41.5 before surgery to 86.8 (P < .001). Radiographic assessments yielded an average Engh fixation score of 20.7. The Kaplan-Meier survival estimate for the average time to follow-up evaluation was 0.98. Based on our patient selection criteria and excellent intermediate clinical and radiographic results, the initial design strategies of the Mallory-Head Porous femoral prosthesis have been confirmed.