Biomechanical Evaluation of the Accuracy in Radiographic Assessment of Femoral Component Migration Measurement after Total Hip Arthroplasty

Introduction: Implant subsidence is one criteria utilized to monitor for prosthesis loosening after total hip arthroplasty (THA) with initial implant subsidence assessment often done utilizing plain radiographs. The specific aim of this study was to identify the most reliable references when using plain radiographs to establish an image magnification with the goals being easy to use, inexpensive, reliable, and accurate. Methods: Two femoral stem implants (stem lengths: 127mm, 207mm) were utilized to simulate hemiarthroplasty of the hip with composite femurs. Different combinations of femoral stem distances from the radiographic film (ODD), source-detector differences (SDD), hip rotation, and hip flexion were elected. Standardized anterior-posterior pelvis for each parameter combination setup were taken. Radiographic measurements (head diameter, stem length, stem seating length) were undertaken five times by three examiners. Radiographic image magnification factors were generated from two references (head diameter and stem length). Radiograph measurement reproducibility and stem seating length errors using these magnification factors were evaluated. Results: High level of repeated measurements reliability was found for head diameter (99 ± 0%) and stem length (90 ± 7%) measurements, whereas seating length measurements were less reliable (76 ± 6%). Stem length error using the femoral head magnification factor yielded 11% accuracy. Stem seating length error using both magnification factors were not reliable (< 7% accuracy). All parameters, except SDD, showed significant effect on calibrated measurement error. Conclusions: Current methods of assessing implant subsidence after THA using plain radiographs are inaccurate or reliable. Clinicians should recognize these limitations and be cautious when diagnosing implant stability using plain radiographs alone

Revision of a Failed Primary Total Hip Arthroplasty following Excessive Reaming with a Medial Cup Protrusion.

Background and Objectives: Atraumatic intrapelvic protrusion of the acetabular component following excessive reaming of the acetabulum with a far medial positioning of the cup is a rare, but serious complication of a total hip arthroplasty (THA). This study analyzes the factors contributing to this uncommon complication and presents the outcome after the revision surgery using the Ganz reinforcement ring combined with a bone graft and plating of the posterior column and/or screws for the anterior column. Materials and Methods: A retrospective case series study with seven patients (four males, mean age 76 ± 10 years (60-86)) that underwent a revision THA within 24 ± 17 days (5-60) after an atraumatic periprosthetic acetabular fracture with a medial cup protrusion was performed. All fractures were reconstructed with a Ganz reinforcement ring and bone graft with a mean follow-up of 1.7 ± 1.7 years (0.5-5). Radiographs were evaluated for the following: (i) cup positioning immediately after the primary THA and the revision surgery, (ii) cup migration in the follow-up, and (iii) fracture healing. Results: The position of the acetabular component as assessed on the postoperative radiographs after the index surgery and before the complete medial cup protrusion showed a cup placement beyond the ilioischial line indicative of a fracture of the medial wall. The revision surgery with the reconstruction of the medial wall with a Ganz reinforcement ring combined with a bone graft restored in the presented cases the center of rotation in the horizontal direction with a statistical significance (p < 0.05). During the follow-up, there was no aseptic loosening with the relevant cup migration or significant change in the position of the acetabular cup at the final follow-up (p > 0.05) after the revision. All seven fractures and bone grafts realized a bone union until the latest follow-up. Conclusions: Following excessive reaming, the acetabular component was placed too far medially and resulted in an intrapelvic cup protrusion. An unstable cup following a fracture of the medial wall was evident on the immediate postoperative radiographs. In the case of the medial wall perforation with an intrapelvic cup protrusion after the primary THA, the reconstruction with a Ganz reinforcement ring was a successful treatment option resulting in the fracture healing and a stable cup positioning. Surgeons should be aware of that rare and probably underreported complication and restore the anatomic center of rotation by treating the defect intraoperatively

Migration pattern of cementless press fit cups in the presence of stabilizing screws in total hip arthroplasty

The aim of this study was to evaluate the initial acetabular implant stability and late acetabular implant migration in press fit cups combined with screw fixation of the acetabular component in order to answer the question whether screws are necessary for the fixation of the acetabular component in cementless primary total hip arthroplasty. One hundred and seven hips were available for follow-up after primary THA using a cementless, porous-coated acetabular component. A total of 631 standardized radiographs were analyzed digitally by the "single-film-x-ray-analysis" method (EBRA). One hundred 'and one (94.4%) acetabular components did not show significant migration of more than 1 mm. Six (5.6%) implants showed migration of more than 1 mm. Statistical analysis did not reveal preoperative patterns that would identify predictors for future migration. Our findings suggest that the use of screw fixation for cementless porous- coated acetabular components for primary THA does not prevent cup migration

Low dose CT-based spatial analysis (CTSA) to measure implant migration after ceramic hip resurfacing arthroplasty (HRA): a phantom study

Implant migration is a predictor of arthroplasty survivorship. It is crucial to monitor the migration of novel hip prostheses within premarket clinical investigations. RSA is the gold standard method, but requires calibrated radiographs using specialised equipment. A commercial computed tomography micromotion analysis solution is a promising alternative but is not yet available for use with monobloc ceramic implants. This study aimed to develop and validate a CT-based spatial analysis (CTSA) method for use with ceramic implants. A phantom study was undertaken to assess accuracy and precision. A ceramic hip resurfacing arthroplasty (HRA) and 20 tantalum beads were implanted into a synthetic hip model and mounted onto a 6-degree of freedom motion stage. The hip was repeatedly scanned with a low dose CT protocol, with imposed micromovements. Data were interrogated using a semiautomated technique. The effective radiation dose for each scan was estimated to be 0.25 mSv. For the head implant, precision ranged between 0.11 and 0.28 mm for translations and 0.34°-0.42° for rotations. For the cup implant, precision ranged between 0.08 and 0.11 mm and 0.19° and 0.42°. For the head, accuracy ranged between 0.04 and 0.18 mm for translations and 0.28°-0.46° for rotations. For the cup, accuracy ranged between 0.04 and 0.08 mm and 0.17° and 0.43°. This in vitro study demonstrates that low dose CTSA of a ceramic HRA is similar in accuracy to RSA. CT is ubiquitous, and this method may be an alternative to RSA to measure prosthesis migration

Revision hip arthroplasty using impacted allograft bone and cement. Studies on prosthetic stability and outcome.

För 50 år sedan började man operera utslitna höftleder och använda konstgjordaledytor som ersättning. Antalet operationer har långsamt ökat och operationen är nu en av de vanligaste i Sverige. En ny höftled leder oftast till total smärtfrihetoch ökad rörelseförmåga under lång tid men ibland kan de insatta delarna lossna. Omoperationer på grund av proteslossning ökar i antal och för närvarande utgör omoperationerna cirka 10 % av alla höftledsoperationer. Dessa är ofta betydligt mer komplicerade än förstagångsoperationer. Benbädden som protesen skulle suttit fast i skadas ofta när protesen lossnar, och detta leder i sin tur till att det är svårare att få den nya protesen att sitta fast.En metod för att återskapa en ny benbädd är att med tät packning av malt benåterskapa benet i vilket proteskomponenterna ska fästa. Detta ben kommer från lårbenshuvuden som andra patienter donerat i samband med sina primära höftprotesoperationer. Metoden med benpackning introducerades på 1980-talet och har i många studier visat sig fungera tillfredställande under lång tid. Nytt ben återskapas och proteserna verkar ha nästan lika stora chanser att lyckas livslångt som en förstagångsoperation. Man har dock kunnat konstatera att höftproteserna efter operationen ofta sjunker ned i lårbenet, mer än vid en förstagångsoperation. Vad man inte vet är dock om proteserna därför har ökad risk för ny lossning eller överhuvudtaget kommer att ge besvär. För att ta reda på detta följde vi 17 patienter hos vilka lårbensdelen hade omopererats med benpackningstekniken. För att med stor precision och känslighet kunna följa hur väl protesen är förankrad i benet använde vi oss av en röntgenteknik (RSA), som kan registrera rörelser ned till 0,2 mm. Vi kunde då se att de fortsatte att långsamt sjunka ned i lårbenet under de 9 år som patienterna följdes men ingenpatient hade sådana besvär av detta att de behövde opereras om under denna tid.En begränsning med att använda ben från andra patienter är dels att tillgångenär begränsad men också den risk för överföring av sjukdomar som finns och som kräver omfattande kontroller av det ben som skall transplanteras. Under en längre tid har man försökt att hitta konstgjorda material som kan ersätta det malda benet. Vi prövar i avhandlingen ett sådant som består av calciumsulfat och hydroxyapatit och som fått namnet ”Cerament”. I en försöksmodell på kanin kunde vi i studie II visa att draghållfastheten, det vill säga vidhäftningen, ökade när ett konstgjort benersättningsmaterial användes.Man har länge diskuterat möjligheten att påverka den mekaniska stabiliteten avdet ben som användes vid benpackning. Detta är särskilt viktigt när man opererar om ledskålar som lossnat från bäckenet då resultaten av dessa är något sämre än när metoden används vid omoperation av lårbensdelen. Clodronate är ett läkemedel som minskar resorption av bentransplantatet. I studie III kunde man iaktta att ledskålen rörde sig mindre efter operationen. Den ökade mekaniska stabiliteten kan leda till förbättrat långtidsresultat.För att kunna bedöma hur patienterna upplever resultatet efter olika höftoperationer har en rad olika frågeformulär med ett antal olika frågor konstruerats. Vi evaluerade ett flertal sådana frågeformulär men ett mycket enkelt, VAS (Visual Analog Scale), visade sig lika bra som mer komplicerade formulär. Kliniskt betyder detta att det i framtida studier blir enklare att jämföra olika operationsmetoder.Sammanfattningsvis visar avhandlingsarbetet att (i) en mindre sjunkning av proteskomponenterna i bentransplantatet inte äventyrar det goda kliniska resultatet, (ii) vidhäftningen av protes mot ben i kaninmodell kan öka med syntetiskt bensubstitut, (iii), läkemedlet clondronate blandat i transplantatet minskar sjunkningen av ledskålen in i bäckenet och (iiii) att en enkel metod, Visual Analog Scale, klarar att gradera det patientupplevda kliniska utfallet lika bra som andra mer omfattande och komplicerade frågeformulär

In vitro biomechanical testing of the stability of primary and revision hip acetabular implants

Hip acetabular stability is the capability of acetabular implants to resist to the forces acting in the acetabulum during patient activities after surgery. If implant motions are sufficiently low, primary stability is achieved and the osteointegration process between the implant and the surrounding bone may occur. In this context, measuring implant motions is essential to predict the implant failure. In clinical practise, these measurements are limited to implant migration, while elastic motions and periacetabular strains are not monitored. So far, to obtain a complete set of stability measurements in vitro testing is the most reliable option. Despite the importance of the experimental analysis, a general consensus about the application of biomechanical tools to solve clinical problems is still missing. The aim of my Ph.D project was to develop and apply reliable in vitro methods to assess the hip acetabular stability in case of primary and revision reconstructions. First, two methodological studies were conducted (1) to define and implement a robust reference frame for the human hemipelvis based on a morphological analysis of this anatomical district and (2) to create a robust procedure to measure the implant motions and the periacetabular strains with the Digital Image Correlation technique. Secondly, I applied these methods to answer the following clinical questions: 1. How do changes in the motor task affect the cup stability and the periacetabular strains? 2. Does the cup medialization affect implant stability? 3. Which is the effect on cup stability of defect reconstructions with an innovative synthetic bone substitute or with human bone graft in revision surgery? All these clinical questions were answered in three experimental studies. In conclusion, this project provided a reliable set of in vitro methods to perform biomechanical testing on human hemipelvis and to assess the stability of acetabular reconstructions by mean of Digital Image Correlation

Cemented Polyethylene Cups in Patients Younger Than 40 Years

Although uncemented cup implants frequently are used in young patients, we believe long-term survival rates of cups in these patients are somewhat disappointing, and therefore we have continued to use cemented cups in primary THA, even in young patients. However, in cases of acetabular bone stock defects, we also use bone impaction grafting. We prospectively followed 130 patients with 175 cemented cups; no patients were lost to followup. The mean age of the patients at surgery was 31 years (range, 16–39 years). An acetabular reconstruction with bone impaction grafting was performed in 84 hips (48%). The minimum followup was 2 years (average, 8.1 years; range, 2.0–18.5 years). Twenty-one of the 175 cups (12%) were revised at an average of 8.1 years (range, 2.0–18.5 years). Reasons for revision were infection (one early, seven late), recurrent dislocations (two), traumatic loosening (one), and aseptic loosening (10). The 10-year survival rate of all cemented cups with end point of revision for any cause was 85%. Survival with end point of aseptic loosening of all cups was 92%. Survival with end point of revision for aseptic loosening was 90% for the cups without impaction grafting and 95% for the cups with impaction grafting. We believe cemented acetabular cups in young patients have acceptable midterm survival; however, in the case of acetabular bone defects, we recommend reconstruction with impaction grafting

Comparison of flanged and unflanged acetabular cup design: An experimental study using ceramic and cadaveric acetabuli

Background and purpose Adequate depth of cement penetration and cement mantle thickness is important for the durability of cemented cups. A flanged cup, as opposed to unflanged, has been suggested to give a more uniform cement mantle and superior cement pressurization, thus improving the depth of cement penetration. This hypothesis was tested experimentally. Materials and methods The same cup design with and without flange (both without cement spacers) was investigated regarding intraacetabular pressure, cement mantle thickness, and depth of cement penetration. With machine control, the cups were inserted into open-pore ceramic acetabular models (10 flanged, 10 unflanged) and into paired cadaver acetabuli (10 flanged, 10 unflanged) with prior pressurization of the cement. Results No differences in intraacetabular pressures during cup insertion were found, but unflanged cups tended to migrate more towards the acetabular pole. Flanged cups resulted in thicker cement mantles because of less bottoming out, whereas no differences in cement penetration into the bone were observed. Interpretation Flanged cups do not generate higher cementation pressure or better cement penetration than unflanged cups. A possible advantage of the flange, however, may be to protect the cup from bottoming out, and there is possibly better closure of the periphery around the cup, sealing off the cement-bone interface

Measurement of migration of a humeral head resurfacing prosthesis using radiostereometry without implant marking: An experimental study

Today, the shoulder joint is the third most commonly replaced joint after the hip and knee joints and the incidence is increasing. In Sweden, 1863 primary Shoulder Arthroplasties and 195 revisions were performed in 2017. The most common diagnoses are Osteoarthritis and irreparable tears of the rotator cuff, with or without arthropathy, often referred to as cuff tear arthropathy. Different Shoulder Arthroplasty (SA) concepts include anatomical total shoulder arthroplasty (TSA), hemiarthroplasty (HSA) and reversed shoulder arthroplasty, but also humeral head resurfacing (HHR) and stemless arthroplasties. All concepts offer pain relief, improvement of function and in quality of life for the different diagnoses. Unfortunately, there are sometimes complications after SA. They involve periprosthetic joint infection, humeral and glenoid fractures, stress shielding, loosening of the glenoid and humeral component but also glenoid erosion and cuff rupture. Some of these complications are most common within 1 year after operation, some after several years, both may lead to a revision. This, together with the fact that new designs of implants and methods of fixation of SA continues to develop, stresses the importance of continuous monitoring of implant survival and follow-up. The overall aim of this thesis was to describe clinical examples of different methods to assess the outcome after Shoulder Arthroplasty. The most common methods are clinical examination, radiographic assessment, Patient Reported Outcome Measure (PROM), National Joint registries, where revisions are an important outcome, but also Clinical Trials. All of these methods are used in one or more of the 4 papers in this thesis and shows the complexity of the topic and the practical work. In paper I we used Radio Stereometric Analysis (RSA) in an experimental set-up and concluded that marker-free RSA can be used for a humeral head resurfacing arthroplasty. In paper II we used data from the Swedish Shoulder Arthroplasty Registry (SSAR) with PROM and revisions to conclude that age is the only factor that affects revision when comparing HSA and HHR. Paper III is a long-time follow-up of a Randomized controlled study where we used radiological assessment, PROM and revisions. The conclusion was that both TSA and HSA develop severe radiological changes 10 year after primary operation. Paper IV is a prospective RSA cohort study where we also evaluated PROM and revisions. The conclusion is that HHR seems to obtain a secure fixation in the humerus, after an initial migration. But also that the prostheses shows continuous glenoid wear. The main conclusion of this thesis is that patient’s operated with SA needs continuous monitoring and several methods may be used to evaluate the outcome