[Challenges of primary hip arthroplasty with high hip dislocation]

BACKGROUND

Endoprosthetic care of high hip dislocation is a surgical challenge. The hip anatomy is greatly altered in these patients, including a rather flat and small acetabulum with impaired bone quality and a relevant chance of a bony defect of the acetabular roof. Additionally, the front coverage and in some cases even the dorsal coverage of the hip are missing. The proximal femur is characterized with an increased antetorsion, a coxa valga position and an enlarged greater trochanter. The medullary cavity is narrowed, the offset is reduced, and the absolut leg length can be enlarged. Further anatomic variations can have been caused by previous surgeries.

AIM OF THE TREATMENT

The goal of the endoprosthetic care is the re-creation of a hip with an anatomic center of rotation, an anatomic offset and equal leg length.

TREATMENT

This can be achieved by a medial shift of the acetabular cup. An acetabular osteotomy including central cancellous bone graft or a bony graft to reinforce the acetabular roof might be necessary. In cases in which an anatomic acetabular cup placement is not possible, a more cranial placement can be done. Further strategies that are essential in several cases are shortening or re-orientation osteotomies of the femur, reaming of the medullary cavity and correct implant selection. Additionally, thorough soft tissue management is of main importance. Generally, the surgery should be well prepared preoperatively.

Low-grade infections as a possible cause of arthrofibrosis after total knee arthroplasty

Purpose

Arthrofibrosis after total knee arthroplasty represents a considerable burden for the patient and a therapeutic challenge for the practitioner. One possible cause discussed in the literature is a low-grade infection. This hypothesis should be examined within the scope of this retrospective study.

Patients and methods

Nineteen patients with clinical symptoms of arthrofibrosis after primary total knee arthroplasty were examined between January, 1999 and January, 2012. Incorrect positioning was radiologically ruled out. All patients were examined clinically (score of Freeman as well as Blauth and Jäger), radiologically (component and leg alignment, patella height according to Insall and Salvati), microbiologically (culture-based procedures), molecular biologically (PCR) and histologically in the course of an open revision of the prosthesis.

Results

According to the score of Freeman et al. (1977), a highly significant improvement in pain (p = 0.007) and in the overall score (p = 0.003) was shown. The knee joint mobility did not change significantly (p = 0.795). PCR was negative in 17 patients. One patient showed a PCR-positive result of the synovial membrane for Corynebacterium spp., while Staphylococcus warneri was detected in the culture. Another patient had a positive result of synovia PCR for Enterococcus cecorum as well as Corynebacterium spp. However, this culture was sterile. In 16 patient samples, no bacterial growth was detectable. Two samples were not evaluable. The main histopathological findings were synovialitis and fibrosis.

Conclusion

The hypothesis of low-grade-infection-induced arthrofibrosis after total knee arthroplasty could not be confirmed in this study. However, based on this small study population the conclusion needs to be confirmed by new and larger studies, ideally prospectively designed including a control group.

Gait Analysis before and after Cycle Training Using a 3D Pedal System

PURPOSE OF THE STUDY In this pilot study, gait analysis was performed before and after training with a 3D pedal system (BIUS1), in order to clarify whether these differences are detectable by gait analysis after a short period of training. MATERIAL AND METHODS Two female and three male subjects were included in a prospective case-control pilot study. The patient and training characteristics were determined. Objective measurement data of the gait were obtained by using a three-dimensional motion analysis system with six infrared cameras and three force plates before and after training with the 3D pedal system. RESULTS The mean age was 36.7 ± 8.7 years and the subjects had a BMI of 21.8 ± 2.4 kg/m 2 . The training time per year was an average of 36.0 ± 11.2 days, with a training workload of 511.4 ± 36.7 km. For time-distance parameters, improvements for the left and right side were obtained for cadence and cycle time after training. In total, there was a reduction in hip abduction angle, and an increase in hip inward rotation, knee outward rotation, and range of the frontal knee angle. CONCLUSIONS Changes in parameters in the gait analysis after a short training interval demonstrate that a 3D pedal system is suitable to produce changes in the gait pattern detectable by gait analysis. Training effects on the supposedly weaker left side can be explained after a brief application of the BIUS1 system. Key words:cycle training, 3D pedal system, gait analysis.

[Functional Comparison of the Outcome after Midvastus and Medial Parapatellar Surgical Approach in Total Knee Arthroplasty]

There are various approaches for total knee arthroplasty (TKA). On the basis of an analysis of the clinical results, it has been demonstrated that the midvastus approach (MV) is advantageous in the early postoperative period compared to the medial parapatellar surgical approach (MPP). The aim of this investigation was therefore to investigate whether the clinical advantage of MV is reflected in the functional outcome. This single blinded, prospective, randomised study was based on a power analysis. Selected randomised patients (MPP = 10, MV = 11) were examined using an instrumental gait analysis system (VICON) preoperatively, and 5 weeks (5 W) and 6 months (6 M) after implantation. The results were compared to a healthy control group (CG = 53). Besides clinical parameters, the primary objective of this study was to measure objective gait parameters; the secondary objective was to record self-assessment (Knee Society score, WOMAC). In both treatment groups, the measurements improved during the investigation period, although most parameters did not reach the CG levels. MV gave better values for the kinetic parameters sagittal knee moment (5 W) and knee power (5 W, 6 M), as well as self-assessment (WOMAC, 6 M). Other clinical parameters were similar in the two groups. In summary, in the early postoperative period, MV led to advantages in function and in subjective behaviour in daily life. From the biomechanical point of view, the MV approach is preferable.

[15-year results following implantation of a stem type AML hip prosthesis]

The trend in arthroplasty of the hip joint to implement new models is partly based on theoretical considerations. In order to verify to which extent the philosophy of individual models is ultimately successful, the presentation of long-term results is required. In the years 1991 and 1992, 433 patients with primary implantation of an uncemented total hip replacement in primary coxarthrosis with a stem type AML (anatomic medullary locking) were treated surgically. 283 of them got a cementless cup type Duraloc. In 311 (71.8 %) patients the mean survival rate of the prosthesis could be determined at a mean follow-up of 15.5 years. 145 (33.5 %) patients were followed up completely both clinically and radiologically. Radiographically, the stem position, changes of the periprosthetic bone of the stem and the cup, as well as the wear of the cups were examined. The cumulative survival rate of the AML stem after 15.5 years was 97.5 %, of the Duraloc cup 88.2 %. The clinical results of the hip scores according to Harris and Merle d'Aubigné were good and excellent and patient satisfaction was very high. There was no relationship between stem position, stress shielding and surrounding lyses at the femur and the acetabulum and survival of stem or cup. There was no correlation between inlay wear and survival of the Duraloc cup. A subsiding of the stem in 2 cases had no effect on the clinical symptoms and quality of life. The press-fit implanted AML stem and the Duraloc cup revealed very good results during the investigation period. Like other implants, the survival rate is limited at the presented implant mainly by the cup.

[Instrumented gait and movement analysis of musculoskeletal diseases]

Instrumented 3-dimensional gait analysis is increasingly being used for the evaluation of movement disorders in orthopedic and neurological musculoskeletal diseases. Due to the high reliability of the measurements the procedures are appropriate for diagnostic purposes as well as for outcome assessment after conservative or surgical interventions. Contrary to conventional clinical assessments gait analysis parameters are able to demonstrate a normal physiological gait pattern that can be achieved with improved kinematic and kinetic parameters. For a suitable application in clinically relevant problems the limitations of the procedures should be taken into account. Due to the high instrumental involvement combined with time and cost expenditure instrumented gait analysis will probably not develop to a clinical routine procedure. Nevertheless, an excellent set of information for answering clinical questions is provided. The present contribution presents selected measurement procedures and technologies and illustrates the wide variety of possibilities with the use of selected clinical examples.

[Evaluation of results after total hip replacement using a minimally invasive and a conventional approach. Clinical scores and gait analysis]

AIM

In a prospective study the results of total hip replacement of patients with coxarthrosis and minimally invasive anterolateral (MIS; n = 48) vs. conventional transgluteal approach (KONV; n = 10) were investigated by means of clinical and functional outcomes. Different clinical scores and gait parameters were compared with each other preoperatively and on average 5 weeks and 6 months postoperatively as well as to a control group (VG; n = 58) of healthy age-matched probands.

MATERIAL AND METHOD

For clinical examination the range of hip motion was determined and the Harris hip score (HHS), the score according to Merle d'Aubigné (MD), the intensity of pain (visual analogue scale - VAS), the SF-36 and the WOMAC arthrosis index have been used. Furthermore, the subjective gait pattern was interpreted and the Trendelenburg sign was analysed. The influence of the implantation on the biomechanics of the joint was estimated with a biomechanical score by analysing the pelvic radiographs. Objective measurement data of the gait were obtained by using a three-dimensional motion analysis system with six infrared cameras and three force plates.

RESULTS

Both groups of patients had good clinical results at five weeks after surgery, especially shown in the significantly better results of the used pain scores. Despite visually inconspicuous gait in both operated groups, the sensitive parameters of the gait analysis showed persistent large deficits. A significant improvement was appreciated six months after surgery, but the level of the healthy probands was not attained at this time. There were no significant differences of any gait parameter between the groups MIS and KONV at any time of examination.

CONCLUSION

Advantages of minimally invasive approaches in total hip replacement which can be found a short time after surgery (like less blood loss, less pain after operation, quicker beginning of mobilisation) were not found in this study 5 weeks later regarding functional outcomes. Persistence of functional deficits, caused by damage to the arthromuscular complex, which occur during the process of the development of the arthrosis, need much more time to recover after surgery, independent of the used approach.

In vivo measurement of polyethylene wear in cementless total hip arthroplasty

PURPOSE OF THE STUDY

Recent years have seen an increase in cementless total hip endoprosthesis (THP) implantations. Easy radiological measurement of wear in cups coated with X-ray dense material, such as metal or ceramics, is not applicable. An alternative technique has thus been developed to radiographically measure wear on cementless spherical implants.

MATERIAL AND METHODS

The authors present a method in which the center of the head of the prosthesis relative to the center of the cup was defined by graphical extrapolation. Changes between the two centers on subsequent images allowed the estimation of wear. Data from 148 randomly selected patients with cemented THP were compared with that from 50 with cementless THP (head diameter always 32 mm). RESULTS Within the cemented group metal heads showed significant more wear than ceramic heads (1.244 mm vs. 0.504 mm). However, calculating the wear rate per year showed no significant difference. No significant differences were observed comparing cemented and cementless group. A comparison of the own results with those of the literature revealed analogous values.

DISCUSSION

Data of the cementless group were comparable with those obtained from conventional wear measurements on cemented hip cups thus validating the technique.

CONCLUSION

The method offers the potential to define wear of metal cups with a polyethylene inlay or with X-ray dense components such as ceramic or metal inlays.

[Radiological and clinical functional examinations 36 months after anterior cruciate ligament repair by a patellar tendon graft]

AIM

The aim of this study was to examine radiological and functional outcome measurements after anterior cruciate ligament (ACL) reconstruction with a bone-tendon-bone (BTB) graft. Investigations included assessment of bony integration conditions regarding the use of bioabsorbable cross pins or a lateral screw for femoral graft fixation. A description of radiological parameters in contrast with IKDC findings is also given.

METHOD

After ACL injuries, 45 patients underwent an ACL repair. For tibial tunnel placement the tibial guide was used in full knee extension. A size-specific femoral aimer was placed by using the transtibial technique in the "over the top" position and the tunnel was reamed with the acorn reamer to 30 mm depth. In 15 patients the BTB graft was fixed with a titanium blunt nose screw from the lateral aspect. The cross-pin technique with bioabsorbable RIGIDFIX implants was used in 30 patients. All patients underwent a follow-up study 36 month postoperatively. Geometric tests of digitised X-rays were performed. For clinical and functional outcome studies of ACL repairs the IKDC score is widely accepted. The score was modified into numeric parameters for 15 selected groups of the IKDC score. All 15 categories were rated from 1 to 4 points (Category A = 4, B = 3, C = 2, D = 1). Clinical and radiological results were statistically analysed.

RESULTS

According to the literature, tunnel placement tibial was physiological in 91% and femoral in 93% of the cases. The femoral tunnel was completely invisible in all patients. No necrosis or pathological findings in former pin holes were seen. In 24 patients the medial compartment space was smaller, but less than 50 % compared to intraoperative X-rays. Even if the mean of tibial tunnel widening was 2.65 mm it was statistically not connected to the results of the IKDC score or X-ray findings of the femoral tunnel. Results in the IKDC groups and categories were seen to be in accord with overall very good and good outcomes. The modified IKDC score showed a mean of 55 points with a range from 46 as lowest (1 patient) and 60 in 4 patients (9%) as highest numeric score.

CONCLUSION

Lateral femoral fixation with screws or bioabsorbable cross-pins shows a biological bony incorporation of a BTB graft. Tibial tunnel widening was seen but without any functional effects. Overall radiological and functional outcomes based on the IKDC score demonstrate results in favour of ACL reconstruction with BTB grafts. Due to the narrowing of the medial compartment space, more radiological outcome studies with a special emphasis on degenerative aspects have to be done.

[Biomechanical influences after implantation of a total hip endoprosthesis on the periprosthetic bone density around the cup]

AIM

The aim of this investigation was to prove how changes of the biomechanical joint load affect the distribution of the bone density around a cementless socket implant as the consequence of a total hip endoprosthesis (THEP).

METHOD

43 patients with different diagnoses were treated with Duraloc cup implants. Using a known biomechanical model, the biomechanical situation, the changes of the joint load and their influence on the local bone density were determined. The periprosthetic bone was divided into three zones. By means of DEXA measurement on the 10th postoperative day as well as at 3 and 12 months after the implantation the change of periprosthetic bone density was analysed.

RESULTS

Following THEP implantation the biomechanical parameters normalised. The mean biomechanical score (with a maximum of 12 points) increased significantly from 6.9 preoperatively to 9.7 postoperatively. Patients with dysplasia coxarthrosis showed the most significant improvement from 2.1 to 8.6 points. The periprosthetic bone density was reduced on an average of 14.4 %, with highest values after 3 months(- 9.5%). The zone- and the diagnosis-related analysis of bone density in combination with analysis of the biomechanical load showed normalised biomechanical parameters and harmonised values of bone density. A remarkable loss of bone was seen in regions with primary high values of bone density. These zones are the lateral cranial edge of the socket in patients with dysplasia coxarthrosis and patients with coxa valga as well as the zones from the lower socket entrance to the socket pole in patients with protrusio acetabuli.

CONCLUSION

In order to ensure a long life-time of the artificial joint, treatment with a THEP of patients suffering from coxarthrosis should lead to a biomechanically optimal reconstruction of the hip joint. Preoperatively existing pathological deformities which, due to mechanical fail loading, lead to an unequal distribution of the bone density must be corrected in order to avoid higher loading of the implant and increased polyethylene abrasion of the socket layer.

[Transgluteal mini-incision. Technique and our own results]

BACKGROUND

A transgluteal mini-incision technique according to the approach of Bauer et al. is described.

MATERIAL AND METHODS

Altogether 194 patients were supplied with a cementless primary total hip endoprosthesis using this approach. Our own results regarding ASA, body mass index, operation time, transfusions, the course of the Hb values, and the use of drugs against pain are described.

RESULTS

The approach does not show any dependence on ASA and BMI. Operation time, blood loss, and use of drugs against pain are not influenced by it. Angled reamers and impactors are mandatory to prevent additional damage of soft tissue. The cosmetic benefit seems to be the only advantage. The approach cannot be recommended for general use.

Osteointegration of hydroxyapatite-titanium implants coated with nonglycosylated recombinant human bone morphogenetic protein-2 (BMP-2) in aged sheep

Osteointegration of metal implants into aged organisms can be severely compromised due to reduced healing capacity of bone, lack of precursor cells for new bone formation, or osteoporosis. Here, we report on successful implant healing in a novel model of aged sheep in the presence of nonglycosylated bone morphogenetic protein 2 (BMP-2). Ewes of 8 to 12 years with significant radiologic and histologic signs of osteoporosis and adipocytic bone marrow received a cylindrical hydroxyapatite-titanium implant of 12 x 10 mm. BMP-2 has been produced as a bacterial recombinant fusion protein with maltose-binding protein and in vitro generation of mature BMP-2 by renaturation and proteolytic cleavage. A BMP-2 inhibition ELISA was developed to measure the in vitro release kinetics of bioactive human BMP-2 from immersed solid implant materials by using Escherichia coli expressed and biotinylated recombinant human BMP-2 receptor IA extracellular domain (ALK-3 ECD). The implants were placed laterally below both tibial plateaus, with the left leg implant carrying 380 microg BMP-2. Both implant types became integrated within the following 20 weeks. The control implant only integrated at the cortical bone, and little new bone formation was found within the pre-existing trabecular bone or the marrow cavity. Marrow fat tissue was partially replaced by unspecific connective tissue. In contrast, BMP-2-coated implants initiated significant new bone formation, initially in trabecular arrangements to be replaced by cortical-like bone after 20 weeks. The new bone was oriented towards the cylinder. Highly viable bone marrow appeared and filled the lacunar structures of the new bone. In mechanical tests, the BMP-2-coated implants displayed in average 50% higher stability. This animal model provided first evidence that application of nonglycosylated BMP-2 coated on solid implants may foster bone healing and regeneration even in aged-compromised individuals.

Röntgenologische Bewertung des Polyethylen-Verschleißes zementfreier Hüfttotalendoprothesen. Radiologic Evaluation of Polyethylene Wear of Cementless Total Hip Endoprosthesis

During the last years increasingly cementless hip endoprostheses have been implanted. Radiological wear measurement of cemented hip endoprostheses for the material couples polyethylene cup-ceramic- or metal head has been established in the literature. However, for cups encased by metal (screwing or pressfit cups), this method of measurement is not applicable. Therefore, a method has been developed to measure wear on radiographs on cementless spherical implants. The data were compared to those, obtained from conventional wear measurements on cemented hip cups. The results indicate that both techniques generate comparable results, thus validating the new technique as being suited for cementless cup implants.

[Determination of the elasticity of the femoral cortex of Adam's arc in patients with osteoarthritis]

In this study, the compressive strength, the compressive force as well as cortical thickness of prismatic specimens from Adam's arc of the femur were determined in patients with osteoarthrosis. Correlations were evaluated between the cortical bone parameters, which depend on age and sex. Supported by histomorphometric data of cancellous bone, the great variability of mechanical properties revealed the variable osteological status prior to implantation of hip endoprostheses. Its eventual consequences for alloarthroplastic surgery had been discussed.

Importance of morphological findings in the progress and treatment of chest wall deformities with special reference to the value of computed tomography, echocardiography and stereophotogrammetry

Patients with chest wall deformities have many particular anatomical, physiological, genetic, biomechanical and psychological characteristics. It is generally recognized that surgical correction of funnel chest and pigeon breast may be done for psychosocial reasons alone. Morphological and dynamic investigations are done to identify the function of the deformed chest wall and to permit objective assessment of the cosmetic and functional outcomes of the operation. There is no universally agreed standard for the diagnosis of funnel chest and pigeon breast. Non-invasive investigations, such as computed tomography (CT), echocardiography (ECG) and stereophotogrammetry (SP), improve the quality of the diagnostic assessment, including evaluation of its functional aspects, without directly influencing the decision to operate, which is still made mainly on subjective grounds. The value of these techniques in the diagnosis of chest wall deformities is assessed and the results of our personal experience are presented.