Very early migration of a calcar-guided short stem: a randomized study of early mobilization and the influence of a calcium phosphate coating with 60 patients.

This study analyzed the migration of a calcar-guided short stem to determine the course of very early migration, as well as evaluated the effect of an additional calcium phosphate (CP) coating on a titanium plasma spray (TPS) coating, which has not been analyzed previously. Sixty patients were enrolled in this study and were treated with the A2 calcar-guided short stem. The implant coating was randomized with either the TPS or an additional CP coating, and radiostereometric analysis was performed with the baseline measurement before initial weight-bearing, along with follow-up examinations at 1 week, 6 weeks, 3 months, and 6 months. Implant migrations were 0.27 mm (standard deviation [SD], 0.13 mm) and 0.74 mm (SD, 1.11 mm) at 1 week and 6 months post-surgery, respectively, and 65% and 87% of the implants reached their final position 1 week and 6 weeks after surgery, respectively. After 6 weeks, 3 months, and 6 months, a significant increase was noted in the migration of the CP coating group vs. that of the TPS coating group. Upon the final observation at 6 months, the groups displayed on average a 0.74-mm migration. Most of the analyzed implants ceased migration within the first week post-surgery, but the CP coating demonstrated a higher and more prolonged migration compared to the TPS coating.

[Tips and tricks of cement removal in the case of revision surgery]. / Tipps und Tricks für die Zemententfernung im Revisionsfall.

BACKGROUND: In Germany, current revision rates after arthroplasty range between 28-37%. In particular, remaining cement residues are causative for additional revision surgery after periprosthetic joint infection, which is why complete cement removal is of high importance. However, the removal of remaining cement residues often confronts the surgeon with technical challenges. Complication-free and complete cement removal requires extensive preoperative preparation in order to develop the best possible surgical strategy. TREATMENT: Special instrument sets to facilitate cement removal in revision cases are available from various manufacturers. In addition to endoluminal approaches, access enhancements such as extended osteotomies exist to facilitate complete cement removal. Finally, the surgeon should be able to give the indication for an intraoperative procedural change after a defined time interval.

[Cement in revision arthroplasty-what about the "glacier effect"? : Case studies viewed from different perspectives]. / Zement in der Revisionsendoprothetik ­ Was ist mit dem "Gletschereffekt"? : Fallbeispiele aus unterschiedlichen Perspektiven betrachtet.

BACKGROUND: The number of operations concerning revision arthroplasty has been increasing continuously in recent years, and it can be assumed that they will continue to increase in the future. If an arthroplasty implant becomes loose, it must be changed. The question often arises as to how the new implant should be fixed in the bone. ADVANTAGES: Revision implants can be inserted into the bone without cement. In the subsequent period, a secondary osseointegration of the implant takes place. Another possibility is to anchor the implant by using bone cement. The advantage of cemented anchorage is that the implant is firmly fixed in the bone, in principle, immediately, and it is possible to fully load the implant directly. Direct postoperative full weight bearing is helpful, especially for older and multimorbid patients, in order to achieve rapid mobilization. PREREQUISITES AND CHALLENGES: When using cement in revision cases, however, there are a few prerequisites and challenges that the surgeon should definitely take into account. In the case of revision, the bone in the former implant bed is often deficient and appears thinned and sclerosed. It is, therefore, important to analyze the bone quality preoperatively on radiographic images and to include it in the planning of the anchoring strategy. In addition, the individual bone quality of the patient must also be taken into account intraoperatively. In any case, it must be clarified whether the basic prerequisites for the sufficient bond strength of the cement with the bone to be formed can still be met. Furthermore, the principles of cementing technique must be strictly observed, and the goal of a perfect cement mantle must be aimed for. If the indication for this is overstated, early loosening of the cemented revision arthroplasty is very likely.

Effects of Iliosacral Joint Immobilization on Walking after Iliosacral Screw Fixation in Humans.

BACKGROUND: Pelvis fractures are commonly stabilized by surgical implants to facilitate their healing. However, such implants immobilize the iliosacral joint for up to a year until removal. We report how iliosacral joint immobilization affects the walking of patients. METHODS: The gaits of patients with immobilized sacroiliac joints after unstable pelvic fracture (n = 8; mean age: 45.63 ± 23.19; five females and three males) and sex- and age-matched healthy control individuals (n = 8; mean age: 46.50 ± 22.91; five females and three males) were recorded and analyzed using a motion capture system. The forces between the tread and feet were also recorded. Standard gait parameters as well as dynamic patterns of joint angles and moments of the lower extremities were analyzed using the simulation software OpenSim. RESULTS: With the exception of hip extensor strength, the monitored joint parameters of the patients showed task-dependent deviations during walking, i.e., plantarflexor force was increased when stepping on an elevated surface, as were hip flexion and extensor moments, knee flexion and extensor moments, as well as ankle dorsiflexion and the associated negative plantarflexor force during stance on the elevated surface. CONCLUSIONS: Iliosacral joint fixation causes reduced forward and upward propulsion and requires an extended range of hip motion in the sagittal plane. Patients show significant mobility limitation after iliosacral screw fixation.

[Three-year revision rate of certified centres for joint replacement according to EndoCert : Risk-adjusted analysis of outcome quality and comparison with other quality assurance systems]. / 3-Jahres-Revisionsrate von zertifizierten EndoProthetikZentren nach EndoCert : Risikoadjustierte Analyse der Ergebnisqualität und Vergleich mit anderen Qualitätssicherungssystemen.

BACKGROUND: The EndoCert initiative does not yet allow a long-term assessment of outcome quality. The assessment cannot be achieved without cooperation with the German arthroplasty registry (EPRD) and other quality assurance infrastructure, such as the quality assurance system of the nationwide healthcare insurance data for inpatient hospital treatment (QSR) by the German local healthcare fund (AOK). Therefore, the quality of care of all certified centres for joint replacement (EPZ) after primary hip and knee arthroplasty was to be examined for the first time. These data were subsequently compared to the data of the EPRD. MATERIALS AND METHODS: In EPZ that provided care to at least one AOK-insured patient in 2016, the risk-adjusted 3­year revision rate and the SMR-value (standardised mortality or morbidity ratio), which is the quotient of the observed and expected revision rate, were analysed as markers for the quality of care. Annual hospital volume, type of centre and audit results were examined as possible influencing factors. RESULTS: In the group comparison, significant differences (p = 0.042) for the SMR value of the 3­year revision rate were demonstrated for hip arthroplasty with regard to the EPZ type. The annual number of primary hip arthroplasties, however, did not influence the 3­year revision rate. For knee arthroplasties, no effect of the defined categories on the 3­year revision rate and its SMR value was observed. The comparison of our 3­year revision rates with those of the EPRD showed similar results for the hip but indicated significant differences for the knee. CONCLUSION: We did not observe a correlation between quality of care and annual hospital volume in certified EPZ. However, different quality assurance procedures can lead to different results with respect to the outcome quality. Therefore, a considerably improved interaction of the German quality systems must be achieved. Participation in the EPRD is not sufficient for this. Rather, a complete report of all arthroplasties must be required, at least with the achievement of a minimum reporting rate per participating hospital. Uniform inclusion and exclusion criteria should be defined.

[Periprosthetic acetabular fractures and defects : Trauma meets ortho]. / Periprothetische acetabuläre Frakturen und Defekte : Trauma meets Ortho.

BACKGROUND: Periprosthetic acetabular fractures are considered to be a severe and challenging complication in total hip arthroplasty. To date, there are no internationally applicable standardized recommendations which can assist orthopedic surgeons and trauma surgeons in the treatment of patients. OBJECTIVE: The aim of this article is to report on the current state of knowledge on periprosthetic acetabular fractures, to present the commonly used classification systems and to demonstrate appropriate treatment algorithms together with personal experiences. MATERIAL AND METHODS: A selective search of the existing literature was carried out and the commonly used classification systems and treatment options for periprosthetic acetabular fractures were compiled and are discussed in relation to the in-house cases. RESULTS: The comparison of the classification systems showed that frequently only fractures which have a purely traumatic origin are included among periprosthetic acetabular fractures. Insufficiency fractures within the framework of acetabular defects, which also belong to the group of acetabular fractures, are frequently included in revision arthroplasty. The management of defects with appropriate implants represents a challenge. By the combination of osteosynthesis and implant replacement, the selection of implants can often be de-escalated. CONCLUSION: Periprosthetic acetabular fractures represent a complex operation for both trauma surgeons and for specially trained orthopedic surgeons, which necessitate a high level of expertise. By the cooperation between trauma surgeons and orthopedic surgeons good treatment results can be achieved and recommendations for the selection of implants can be made.

Is the strain pattern of conventional stems negatively affected by a previously short stem THA? An experimental study in cadavaric bone.

BACKGROUND: A short stem hip arthroplasty can be revised in many cases using a conventional stem. Furthermore, in some cases the implantation of a short stem is intended, but intraoperatively reasons may lead to the decision to implant a conventional stem after previous preparation of a short stem. OBJECTIVE: In both cases it is questionable if the anchorage of a conventional stem is negatively affected by the previous preparation of a short stem. In clinical practice mid- or long-term follow up for these special cases hardly exist. METHODS: The strain patterns for the conventional Bicontact stem in primary implantation and after preparation of the proximal femur for a METHA short stem were tested biomechanically in three pairs of cadaveric femora. RESULTS: The strain patterns for the conventional Bicontact after preparation of the METHA short stem were similar to conditions after testing the conventional stem in primary conditions. CONCLUSIONS: These data lead to the consequence that in clinical practise the implantation of a conventional stem after preparation of a short stem and even after revision of a short stem is possible without increased risk of loosening or long-term stress-shielding.

Evaluation of the standard procedure for the treatment of periprosthetic joint infections (PJI) in Germany - results of a survey within the EndoCert initiative.

BACKGROUND: The periprosthetic joint infection (PJI) is a severe complication in the field of arthroplasty. Despite the rising number of primary joint replacements, no unified therapeutic standard has been established for the treatment of PJI yet. METHODS: A survey on the principles of treatment of PJI in Germany was conducted. A total of 515 EndoProthetikZentren (EPZ) were included, resulting in a response rate of 100%. RESULTS: For early infections 97.6% of the centers use prosthesis-preserving procedures (DAIR). A one-stage exchange was implemented by less than 50% of the centers. If implemented, this treatment entails a prior selection of patients for a successful treatment. The two-stage exchange is performed in all centers, and most centers proceed with the implantation of a cemented spacer between stages. 75% of the centers proceed with a center-based concept for the treatment of PJI. CONCLUSION: The aim of a uniform PJI standard at the centers has not yet been fully achieved. Further improvements within the certification were initiated. The most relevant treatment options in Germany are displayed. The two-stage revision with a cemented spacer is the most widely implemented treatment. This exposition of principles could help for the further development of standardized treatment guidelines and definitions.

[Custom-made acetabular implants in revision total hip arthroplasty]. / Individuell angepasster Beckenteilersatz in der Hüftgelenksrevision.

BACKGROUND: Management of acetabular bone loss is a demanding problem in revision total hip arthroplasty. OBJECTIVES: The aim of this review is to introduce and discuss the results and the advantages and disadvantages of custom-made implants as a treatment option for severe acetabular bone defects. MATERIALS AND METHODS: A selective review of the existing literature of custom made acetabular implants was performed on PubMed. RESULTS: Studies showed good clinical and radiological outcomes of custom made acetabular implants and a survival rate of more than 90%. CONCLUSION: Custom-made acetabular implants are a reliable treatment option for severe acetabular defects and allow the reconstruction of the centre of rotation of the hip. The costs of these implants are high and planning is time consuming.

A short stem with metaphyseal anchorage reveals a more physiological strain pattern compared to a standard stem - an experimental study in cadavaric bone.

PURPOSE: The proposed advantages of short stem hip arthroplasties are bone preserving strategies and less soft tissue damage. Bone preserving strategies do not only include a more proximal resection of the femoral neck, but especially for short stem hip arthroplasties with predominantly metaphyseal fixation a presumed more physiologic load transfer and thus a reduction of stress-shielding. However, the hypothesized metaphyseal anchorage associated with the aforementioned benefits still needs to be verified. Unfortunately, mid- to long-term clinical studies are missing. METHODS: Therefore, the METHA short stem as a short stem with proposed metaphyseal anchorage and the Bicontact® standard stem were tested biomechanically in three pairs of cadaveric femora while strain gauges monitored their corresponding strain patterns. RESULTS: For the METHA stem, the strains in all tested locations including the region of the calcar were similar to conditions of cadaver without implanted stem. The Bicontact stem showed approximately half of strain of the non-implanted cadaveric femura with slightly increasing strain from proximal to distal. CONCLUSIONS: Summarizing, the current study revealed primary metaphyseal anchorage of the METHA short stem and a metaphyseal-diaphyseal anchorage of the Bicontact stem.

Outcomes of Noninvasively Treated Idiopathic Toe Walkers.

Idiopathic toe walking (ITW) causes a common problem in pediatric orthopaedics. In the literature, numerous treatment options have been reported, but consensus about the management of ITW is still missing. The aim of the current study was to evaluate conservative treatment with pyramidal insoles. A total of 193 patients underwent conservative treatment between January 2010 and June 2013. Mean age at the beginning of the treatment was 7.75 ± 0.23 years (range 2.0-17.0 years). For all patients, demographic data, comorbid diseases, passive range of motion (ROM), persistent toe walking, and performed operations were retrospectively evaluated. Following operative treatment was defined failure. Eight (4.15%) patients underwent Achilles tendon lengthening operation after mean therapy time of 2.72 years (range 0.1-7.0 years), 174 cases were treated successfully (90.16%). In 50 cases, toe walking suspended completely after mean therapy time of 2.83 years. In cases of failure, patients were older at diagnosis and at the beginning of the treatment. Mean passive ROM increased over the time. In cases of failure, ROM decreased from the first to the second examination. Conservative treatment of ITW using pyramidal insoles can be effective. Ankle dorsiflexion significantly improved in the patients who were successfully treated. Therapy should start early. A decrease of ROM under therapy should lead to critical revisal of individual therapy. Levels of Evidence: Therapeutic, level IV: Case series.

[Short Stem, Straight Stem or Anatomical Stem: Free Decision or Recommendations?] / Kurzschaft, Geradschaft, anatomischer Schaft: freie Wahl oder Empfehlungen?

The main goal of total hip arthroplasty is to reduce pain. But function, stability, and longevity are also of major importance. Since the inauguration of modern total hip arthroplasty by Charnley, the designs of stems has undergone many changes. The following paper concerns the straight stem, the anatomical stem and the short stem in total hip arthroplasty. It attempts to answer the question as to whether there is a recommendation for the use of a special stem. The straight stem is the oldest of these stem types. Depending on the particular design, the anchorage of these stems may lie in the metaphyseal or the diaphyseal parts of the femur. The closer the contact of the stem is to the diaphyseal part, the greater is the risk of stress shielding. The anatomical stem attempts to match the geometry of the proximal femoral endosteal. This can be helpful to reconstruct the natural load bearing but has also limitations in fitting. The short stem was designed to achieve an anatomical pattern of stress distribution, resection of less bone and reduction in thigh pain. There are additional differences between the designs. But not only the stem design has to be considered. The proximal part of the femur exhibits a great variety of morphologies. Whereas younger patients mostly have secondary osteoarthritis due to deformities, elderly patients may have changes in morphology due e.g. osteoporosis. Depending on these patient-specific factors and bearing biomechanical aspects in mind, the surgeon must choose the stem design. This may require different stem designs with different mechanisms of fixation.

Factors affecting operative time in primary total hip arthroplasty: A retrospective single hospital cohort study of 7674 cases.

BACKGROUND: Total hip arthroplasty (THA) is one of the most common orthopedic procedures in developed countries, and the high volume of surgery and the socioeconomic burden of failures demand continuous optimization. Operative time has been identified as a significant independent factor influencing the clinical outcome of THA. OBJECTIVE: The aim of this study was to analyze factors influencing the operative time for THA in a large, single-center cohort. METHODS: A consecutive series of 7,674 cases undergoing primary THA was identified, and after multiple imputation of missing values, univariable and multivariable linear regression analyses were performed. RESULTS: In the univariable analysis, all factors showed significant influences on operative time, while multivariable regression analysis revealed that sex, a diagnosis of hip dysplasia and small femoral component size did not reach significance. Younger age, an underlying diagnosis other than osteoarthritis or hip dysplasia, a large stem size, usage of a conventional stem rather than a short stem, a larger cup size and a cemented fixation technique, however, remained significantly influential in terms of a longer operative time. CONCLUSIONS: This study identified risk factors for longer operative time that in turn is associated with a higher rate of periprosthetic joint infection and impaired clinical outcome. Our findings could help to refine scheduling of total hip arthroplasty procedures in times of increasing cost and efficiency pressure.

The outcome of the partial resurfacing arthroplasty of the hip shows high numbers of failures and conversion to total arthroplasty.

PURPOSE: Local cartilage and bony defects, which are too large for joint preserving cartilage treatment are difficult to treat. The implantation of a mini-resurfacing implant (Hemicap®, 2med, Hamburg, Germany) may be a possible alternative treatment for these patients. This partial replacement fills the defect and restores a smooth and continuous articular surface. The aim of this study was to determine short- to midterm results of the treatment of local cartilage defects of the femoral head using the Hemicap®. METHODS: Since 04/2011 16 patients with osteonecrosis of the femoral head greater ARCO stage II or local femoral cartilage lesions (< 35 mm) were treated with the implantation of the Hemicap® implant. A clinical and radiological follow-up was conducted. RESULTS: The clinical results showed a significant improvement of the function and pain of the hip according to the Harris Hip Score from 56 (±14) preoperative to 77 (±15) post-operative 25 months after implantation of the Hemicap®. In the meantime, in four patients the Hemicap® had to be converted to a total hip arthroplasty due to loosening, progredience of the osteonecrosis or degeneration of the acetabulum. CONCLUSIONS: The implantation of the mini-resurfacing implant Hemicap® seemed to be an alternative treatment for local cartilage defects of the femoral head to postpone the implantation of a total hip arthroplasty. However, the clinical outcome seems to be inferior to total hip arthroplasty. Furthermore, due to a high rate of conversion to total hip arthroplasty (25%) the application of this implant is questionable. If the implant is considered as a treatment option at least patient selection and enlightenment for this treatment with the high risk of failure and progression of osteoarthritis is very important.

The Influence of Tribological Pairings and Other Factors on Migration Patterns of Short Stems in Total Hip Arthroplasty.

Over the last decade, the number of short stem total hip arthroplasty procedures has increased. Along with the possible benefits associated with short stems is a smaller implant-bone contact surface, which may have a negative influence on primary stability and impair osseointegration. Previous studies observed migration of short stems, especially within the first three months. The variables that influence migration in short stem hip implants remain unknown. Therefore, the purpose of this study was to associate the migration of short stems with its possible influencing variables. Migration data from two different short stem studies were retrospectively analyzed. Migration within the first two postoperative years was determined by model-based Roentgen stereophotogrammetric analysis. Migration was correlated to bearing couple, type and size of stem, size of acetabular cup, and age, gender, weight, and height of patients using a multiple factor analysis. Eigenvalue analysis explained 80.7% of the overall variance for the first three dimensions. The four most dominant variables in the first dimension were weight, stem size, acetabular cup size, and patient height (correlations of 0.81, 0.80, 0.71, and 0.70, resp.). None of the analyzed parameters (bearing couple, type and size of stem, size of acetabular cup, and age, gender, weight, and height of patients) affected the migration pattern of short stem THA with primary metaphyseal fixation.

Hip Arthroplasty in Obese Patients: Rising Prevalence-Standard Procedures?

We examined our experience and, in particular, complications associated with total hip arthroplasty in obese and morbidly obese patients. We prospectively gathered 50 patients in a matched control series including 25 obese and morbidly obese patients. All patients were operated using the direct lateral approach and standard postoperative protocols. Operating room time, complications, dislocations, blood loss, cup position and clinical parameters using the Harris Hip Score and the Western Ontario and McMaster Universities Arthritis Index results were compared. Although there were some significant differences in clinical outcomes, standard procedures yielded good overall results and an acceptable rate of complications. Details approaching this patient entity are being discussed.

Use of single-representative reverse-engineered surface-models for RSA does not affect measurement accuracy and precision.

Implant migration can be accurately quantified by model-based Roentgen stereophotogrammetric analysis (RSA), using an implant surface model to locate the implant relative to the bone. In a clinical situation, a single reverse engineering (RE) model for each implant type and size is used. It is unclear to what extent the accuracy and precision of migration measurement is affected by implant manufacturing variability unaccounted for by a single representative model. Individual RE models were generated for five short-stem hip implants of the same type and size. Two phantom analyses and one clinical analysis were performed: "Accuracy-matched models": one stem was assessed, and the results from the original RE model were compared with randomly selected models. "Accuracy-random model": each of the five stems was assessed and analyzed using one randomly selected RE model. "Precision-clinical setting": implant migration was calculated for eight patients, and all five available RE models were applied to each case. For the two phantom experiments, the 95%CI of the bias ranged from -0.28 mm to 0.30 mm for translation and -2.3° to 2.5° for rotation. In the clinical setting, precision is less than 0.5 mm and 1.2° for translation and rotation, respectively, except for rotations about the proximodistal axis (<4.1°). High accuracy and precision of model-based RSA can be achieved and are not biased by using a single representative RE model. At least for implants similar in shape to the investigated short-stem, individual models are not necessary. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:903-910, 2016.