Implant fracture of modular revision stems is a major complication after total hip arthroplasty revision (rTHA). Studies looking at specific modular designs report fracture rates of 0.3% to 0.66% whereas fractures of monobloc designs are only reported anecdotally. It is unclear whether the overall re-revision rate of modular designs is higher and if, whether stem fractures or other revision reasons are responsible for this elevation.

All revisions within 5 years after implantation of a revision stems (n₀=13,900; n₅=2506) were analysed using Cox regression with design (modular: n=17, monobloc: n=27), BMI, Sex and Elixhauser Score as independent variables. One stage and two stage revisions were analysed separately (1-stage: modular n= 7,102; monobloc n= 4,542; 2-stage: 1,551 / 704). The revision volume of the hospitals was also considered (low: <20 revisions, medium: 21–50 revisions, high: >50 revisions).

For the 1-stage revisions, the re-revision risk after 4 years was 14,3% [13.2%, 15.5%] for monobloc and 17.4% [16.40%, 18.40%] for modular stems (p< 0.001). Stem fracture was the reason for re-revision in 2.4% of the modular (fracture rate 0.42%) and 0.6% of the monobloc revisions. The difference in re-revision rates between the designs was mainly due to differences in dislocation and stem loosening. For the 2-stage revisions, the revision risks for either design were similar (21.7% [18,5%, 25.4%] vs. 23.0% [20.8%, 25.4%]; p=0.05). Patient characteristics influenced the comparison between the two designs in the 1-stage group but very little in the 2-stage group.

Modular revision stem fractures only contribute very minor to re-revision risk. In 2-stage revisions, no difference in overall re-revision rates between designs was observed. This might indicate that the differences observed for 1-stage procedures are due to differences between the patient cohorts, not reflected by the parameters available or surgeon choice.

Recent case reports have described V40 taper failure with clinically relevant adverse reaction to metal debris (ARMD). The real incidence of V40 taper damage and potential consequences are currently unclear, however. Aim of this study is therefore, to evaluate the long-term incidence of pseudotumors in a consecutive series of THA with V40 taper and identify potential influencing factors.

From 2006 to 2007 a total number of 120 patients (127 hips) received either an uncemented (Accolade©) or cemented hip stem (ABGII©), both with V40 taper (Stryker© Mahwah, New Jersey, USA). They all were combined with 36 mm Vitallium (CoCrMo) heads and uncemented cups (Trident©) with XLPE inlays. 11,2 +/− 0,5 years post-op 82 patients with 87 hips (mean age 74 years, 58 % female) underwent clinical (PROMs) and radiographic evaluation. In 71 patients (75 hips) MARS- MRI of the hip was performed. 38 patients were lost to follow-up. In 81 patients (86 hips) chrome and cobalt levels were determined.

MRI-investigation revealed 20 pseudotumors (26%) and 18 of them had a diameter of >2cm. Patients with pseudotumors had significant higher median cobalt ion levels compared to those without (2,85 μg/l vs. 1,32 μg/l; p=0,022) and a significant correlation between pseudotumors and cobalt levels was found. Radiographic osteolysis was associated with pseudotumors as well (p= 0,014). Neither approach, BMI, gender, age, type of stem, head length, inclination nor heterotope ossification showed a significant correlation to pseudotumor occurrence.

Due to the high incidence of local ARMD in in asymptomatic patients with V40 taper and metal heads we recommend regular post-operative follow-up investigations including routine metal ion screening and consecutive MRI investigation upon elevation.

Due to well-known complications of metal-on-metal hip resurfacing arthroplasty the indication for this procedure has significantly decreased over the past years. As a high number of patients is currently living with resurfacing implants, however, there is a clear need for information about the longterm results and especially about the rate of local as well as systemic adverse effects.

We retrospectively reviewed our first 95 patients who had 100 consecutive BHR hip resurfacings performed from 1998–2001. Median age at surgery was 52 years (range, 28–69 years); 49% were men. After a mean follow-up period of 16.1 years (range 15.2 – 17.6 years) we assessed survival rate (revision for any reason as endpoint), radiographic changes and patient-related outcome in patients who had not undergone revision. In addition we measured whole blood concentrations of cobalt at follow-up.

17% of our patients in the original cohort were lost to follow-up. In the remaining patients the 16-year survivorship was 80.1%. The overall survival rate was slightly higher in males (80.6%) than in females (77.1%). The WOMAC overall score showed a median value of 91.7 points (range 35.4 – 100). Median whole blood ion levels were 1.9 µg/L for cobalt (0.6 – 140.2 µg/L), 14.9% of patients showed elevated levels. The number of patients with relevant radiographic signs of local adverse reactions to metal debris was relatively low.

In contrast to earlier reports and very few other longterm studies our results show an unsatisfactory performance of resurfacing. In particular the outcome of male patients deteriorated between 10 and 16 years of follow-up. Although only a small number of patients shows relevant elevation of metal-ion levels, the clinical relevance has still to be determined.

Background: As many as 20% of all patients after total knee arthroplasty (TKA) are not satisfied with their result. Different factors affecting clinical outcome include leg alignment, rotational alignment, soft tisssue-balancing, the femoro-patellar joint, and patient-related factors. The purpose of this study was to assess relationships between prosthesis rotational alignment, function score and knee kinematics after TKA.

Materials and Methods: From initially eighty patients with a cemented, unconstrained, cruciate-retaining TKA with a rotationg platform without patellar resurfacing seventy-three patients were available for post-operative physical and radiological examination after a median of 20 months follow-up.

Results: Nine patients had more than 10° rotational mismatch between the femoral and tibial component in the postoperative CT-scans. These patients were not different from the remaining 64 patients in the KSS Knee score (both groups 89 points at follow-up) and EQ 5D VAS (65 points vs 70 points at follow-up) but showed significantly worse results in the KSS Function score. While the normal patients with less than 10° rotational mismatch impoved from a median preoperative 55 points to a median 70 points at follow-up, the group with more than 10° mismatch deteriorated from a median 60 points preoperatively to a median 50 points at follow-up (p = 0.001).

For seven of these nine patients, kinematic analysis was available during passive flexion from approximately 0° to 120°. There were no substantial differences in the average range of total axial rotation achieved in this group compared to the normal group, but the pattern of motion during that range was quite different. While external rotation steadily increased with knee flexion in the normal group, there was internal rotation between 30° and 80° of flexion in the group with more than 10° rotational mismatch.

Conclusion: Rotational mismatch between femoral and tibial components exceeding 10° resulted in different kinemtics after TKA. This might contribute to worse clinical results observed in those patients and should therefore be avoided.

Background: Correct rotational alignment of the femoral and tibial component is an important factor for successful TKA. The transepicondylar axis is widely accepted as a reference for the femoral component. There is no such reference for the tibial component. CT scans were used in this study to measure which tibial landmark most reliably reproduces a correct femoro-tibial rotational alignment in TKA. Furthermore, the impact of computer-assisted navigation on rotational alignment is investigated.

Materials and Methods: After informed consent, 80 patients were randomized to receive either navigated or conventional TKA. All patients received a cemented, unconstrained, cruciate-retaining TKA with a rotating platform. CT scans were performed 5–7 days postoperatively but before discharge. The rotational variance between the femoral and tibial components was measured.

Results: There was notable rotational variance between the femoral and tibial components in both groups. In the navigated group, the median variance was 1.2° relative external rotation of the femur (range: 16.2° relative external to 12.7° relative internal rotation of the femur). In the conventional group, the median variance was 1.7° relative internal rotation of the femur (range: 9.0° relative external to 14.4° relative internal rotation of the femur). Using the medial third of the tuberosity as reference for tibial rotational alignment, 67.5% of all TKA had a femoro-tibial variance within ± 5°, 85% within ± 10° and 97.5% within ± 20°. Using the medial border of the tibial tubercle as reference this variance was greater, 3.8% had a femoro-tibial variance within ± 5°, 15% within ± 10° and 68.8% within ± 20°.

Conclusion: Using fixed bone landmarks for rotational alignment leads to a notable variance between femoral and tibial component. Computer-assisted navigation did not reduce this variance.

Referencing the tibial rotation on a line from the lateral border of the medial third of the tibial tubercle to the center of the tibial tray resulted in a better femoro-tibial alignment than using the medial border of tibial tubercle as landmark. Surgeons using fixed bearings with a high conformity between the inlay and the femoral component should be aware of this effect to avoid premature polyethylene wear.

Background: Computer-assisted navigation systems are supposed to improve the precision of implant positioning and therefore the longevity of the knee arthroplasty. Several studies have demonstrated a better mechanical axis or axial component alignment in navigated compared to conventional TKA at least less outliers from a range of 3° of varus or valgus. It is still unclear wether navigation can improve rotational alignment.

Materials and Methods: After informed consent 80 patients were randomized to navigated or conventional TKA. In all patients, a cemented, unconstrained, cruciate-retaining TKA with a rotating platform was implanted. A full-length standing and a lateral radiograph and CT Scans of the hip, knee and ankle joint were done 5 to 7 days postoperatively before discharge.

Results: The navigated group showed a median deviation from the mechanical axis of 1,5° with a range between 5,9° valgus and 4,6 varus malalignment. The conventional implanted arthroplasties showed a median deviation from the mechanical axis of 1,6° with a range between 5,9° valgus and 7,2° varus malalignment. 5 navigated and 7 conventional implanted arthroplasties were outside a tolerance level of 3°.

The femoral component showed a median deviation from the transepicondylar axis of 1,7° (range: 3,1° external rotation to 4,4° internal rotation) in the navigated group and of 1,0° (range: 3,4° external rotation to 4,3° internal rotation) in the conventional implantations.

The tibial component showed a much greater range of rotational deviation from the medial third of the tuberosity in median 5,3° (range: 14,9° external rotation to 26° internal rotation) in the navigated group and 4,8° (range: 6,5° external rotation to 23,8° internal rotation) in the conventional implantations.

Conclusion: We could not find a difference between Computer-assisted navigation and conventional implantation for rotational alignment of the femoral or tibial component. While the deviation from the transepicondylar axis was quite low and nearly all implantations were within a range of 3° of internal and external rotation there was a considerable range of deviation for the tibial rotational alignment.

Major drawbacks associated with autologous bone grafting are the risk of donor site morbidity and its limited availability. Sterilized bone allograft, however, lacking osteoinductive properties, carries the risk of graft failure resulting from insufficient osseointegration of the graft.

The aim of this study was to vitalize bone allograft with human osteoprogenitor cells under GMP-conform conditions. For this purpose we investigated proliferation, osteogenic differentiation and large-scale gene expression of human MSCs cultured three-dimensionally on peracetic acid (PAA)-treated spongious bone chips.

MSCs were isolated from healthy donors (N=5) and seeded onto PAA-treated spongious bone samples (~5×5×5 mm, DIZG, Germany) under GMP-conform conditions. Proliferation (total protein assay), osteogenic differentiation (cell-specific ALP activity assay, quantitative gene expression analysis of selected osteogenic marker genes), and morphology were assessed. RNA was isolated and microarray analysis was performed using the PIQORTM Stem Cell Microarray system (Miltenyi Biotec) including 942 target sequences.

Increasing cellularity was observed during the 42 d observation period while cell-specific ALP activity peaked at day 21. Effective proliferation and adhesion of human MSCs on PAA-treated spongious bone was confirmed by histology, scanning electron and confocal laser scanning microscopy. Gene expression of early (Runx-2), intermediate (ALP), and late (osteocalcin) osteogenic marker genes was present during 42 days of cultivation. Microarray analysis of MSCs cultivated on bone allograft versus 2-D tissue culture demonstrated temporal upregulation of genes involved in extracellular matrix synthesis (e.g., matrix metalloproteases, collagens), osteogenesis (e.g., BMPR1b, Runx-2) and angiogenesis (angiopoietin, VEGF).

PAA-treated spongious bone allograft is a biocompatible carrier matrix for long-term ex vivo cultivation of MSCs as observed by favorable proliferation, cell distribution, gene expression profile, and persisting osteogenic differentiation. GMP-grade vitalisation of bone allograft by cultivation with autologous MSCs represents a promising clinical application for the treatment of osseous defects.

Metallic implants are widely used in orthopedic, oral and maxillofacial surgery. Durable osseous fixation of an implant requires that osteoprogenitor cells attach and adhere to the implant, proliferate, differentiate into osteoblasts, and produce mineralized matrix. We previously observed that human mesenchymal stem cells (MSCs) adherent to smooth tantalum (Ta) surfaces demonstrated superior biocompatibility compared with titanium (Ti) coatings.

The aim of the present study was to investigate the interactions between MSCs and smooth surfaces of Ta and by means of whole-genome microarray technology.

Immortalized human mesenchymal stem cells were cultivated on smooth surfaces of Ti and Ta. Total RNA was extracted after culturing for 1, 2, 4, and 8 days and hybridized to Affymetrix whole-genome microarrays (N=16). Replicate arrays were averaged and the ratios of gene expression by MSCs cultivated on Ta versus Ti coating were calculated. Absolute fold differences were also calculated and lists of upregulated genes were generated. Moreover, gene Ontology (GO) annotation analysis of differentially regulated genes was performed.

For both Ta and Ti coatings, the vast majority of genes were upregulated after 4 d of cultivation. Genes upregulated by MSCs cultivated on Ta coating for 4 d were annotated to relevant GO terms. Ti-regulated GO annotation clusters were predominantly transcription-related. By using the K-means clustering algorithm, 10 clusters containing more than 5 genes were identified. Moreover, various genes related to osteogenesis and cell adhesion were upregulated by MSCs exposed to Ta surface.

Microarray analysis of MSCs exposed to smooth metallic surfaces of both Ta and Ti generally showed a huge increase in transcriptional activity after 4 d of cultivation. According to GO annotation analysis Ta coating may induce increased adhesion and earlier differentiation of MSCs compared to Ti surface making Ta a promising biocompatible material for bone implants.

The aim of our study was to compare the precision and effectiveness of a CT-free computer navigation system against conventional technique (using a standard mechanical jig) in a cohort of unselected consecutive series of hip resurfacings.

One hundred and thirty nine consecutive Durom hip resurfacing procedures (51 navigated and 88 non-navigated) performed in 125 patients were analysed. All the procedures were done through a posterior approach by two surgeons and the study cohort include the hip resurfacings done during the transition phase of the surgeons’ adoption of navigation.

There were no significant differences in the gender, age, height, weight, BMI, native neck-shaft angles, component sizes and blood loss between the two groups. There was a significant difference in the operative time between the two groups (111 minutes for the navigated group versus 105 minutes for the non-navigated group; p=0.048). There were 4 cases of notching in the non-navigated group and none in the navigated group. There were no other intra-operative technical problems in either of the groups nor were there any femoral neck fractures.

No significant difference was found between the mean post-operative stem-shaft angles (138.5° for the navigated group versus 139.0° for the non navigated group, p=0.740). However there was a significant difference in the difference between the planned stem-shaft angle versus the post-operative stem-shaft angle (0.4° for the navigated group versus 2.1° for the non-navigated group; p=0.005). There was significantly more scatter in the difference between the post-operative stem-shaft angle and the planned stem-shaft angle in the non-navigated group (standard deviation = 3.6°) when compared with the navigated group (standard deviation = 0.9°; Levene’s test for equality of variances = p≤0.01). No case in the navigated group showed a post-operative stem-shaft angle of more than 5° deviation from the planned neck-shaft angle when compared to 33 cases (38%) in the non-navigated group (p≤0.001). While only 4 cases (8%) in the navigated group had a postoperative stem-shaft angle deviating more than 3° from the planned stem-shaft angle, this occurred in 50 cases (57%) in the non-navigated group (p≤0.001).

Hip resurfacing is a technically demanding procedure with a steep learning curve. Varus placement of the femoral component and notching have been recognised as important factors associated with early failures following hip resurfacing. While conventional instruments allowed reasonable alignment of the femoral component, our study has shown that use of computer navigation allows more accurate placement of the femoral component even when the surgeons had a significant experience with conventional technique.

For the prevention of premature osteoarthritis of the hip, the periacetabular osteotomy (PAO) of Ganz has become a common procedure. Though being a powerful method for obtaining large correction angles its drawback is the need for a broad exposure, resulting in more or less disfiguring scars. We modified the surgical approach to PAO by using two small skin incisions and reduced the extent of deep exposure by leaving the rectus femoris tendon in place and avoiding larger peri-articular deep soft tissue release.

The aim of this study is, to compare the early clinical and radiographic results of this less invasive approach with the conventional Smith-Peterson approach.

Patients and Methods: Between 01/04 and 05/05 22 consecutive PAO were performed through a conventional Smith-Peterson approach (group A). After introducing the less invasive technique 22 PAO were performed between 09/04 and 11/05 (group B). All patients were operated by the same experienced surgeon. Patients age ranged from 14 years to 46 years (mean age 26 years). Clinical (i.e. Harris-Hip-Score, Vancouver Scar Scale) and radiographic examinations (i.e. CE-angle) were performed preoperatively and postoperatively at an average follow-up of 16 months (range 6–29 months).

Results: Mean CE-angle correction in group A was 17° and in group B 23°. Functional improvement, as rated by the preoperative to postoperative Harris-Hip-Score-difference, was 15 points in group A and 22 points in group B. After the less-invasive approach, scars were considerable smaller and better-rated by the Vancouver Scar Scale (3 versus 4 after conventional surgery). The number of transient lateral cutaneous femoral nerve lesions was the same in both groups. The average time of surgery was 135 min. in group A and 153 min. in group B.

Conclusion: A smaller skin incision and limited soft tissue exposure improves cosmetic results after PAO without influencing the extent of acetabular correction negatively. The early and mid-term postoperative functional results, however, could not be significantly improved by the less invasive approach.

Background: High volumetric wear of polyethylene was the main factor in periprosthetic bone resorption and the failure of historic metal or ceramic on polyethylene hip resurfacing prosthesis. Metal on metal devices reduce the wear substantially and may solve this problem. The present study describes the clinical and radiographic results of our first 300 hips treated with the Birmingham Hip Resurfacing (BHR, Midland Medical Technologies, U.K.).

Methods: Between September 1998 and May 2003, 300 BHR were implanted in 262 patients. The patients had an average age of 49 years, 56% were men, 58% had a diagnosis of a CDH, 19% of osteoarthritis and 11% of avascular necrosis. Clinical and radiographic follow-up was performed at three months postoperatively and yearly thereafter.

Results: The average duration of follow-up was 2.4 years (1 to 5 years). We achieved a follow-up rate of 97%. Mean Harris Hip Score increased from 51 points pre-operatively to 91–92 points after one to five years, Total range of motion increased from 136 to 220. 6 prostheses had to be revised due to malposition (2), infection (2), neck fracture (1) and inguinal pain (1). Acetabular radiolucencies were observed in 3% in one zone, femoral radiolucencies in 5% in one to three zones around the stem. No patient showed radiolucency lines in all zones or migration.

Conclusions: In our opinion the cementless press fit cup, the low wear metal-on-metal bearing and the conservative implantation technique of the BHR at least fundamentally improves the known disadvantages of the historic Resurfacings. Our preliminary experience is encouraging, but has to be proofed in long-term observations.

In addition to “conventional” total hip replacement with cemented or cementless stems more recently different implant designs have been proposed by Orthopaedic Surgeons in Europe and US. Especially surface replacement and short stem prosthesis are believed to overcome the disadvantages of conventional THR in younger patients.

The symposium “MINIMAL DEVICE OR REPLACEMENT FOR THE HIP” is trying to summarize current implant philosophies and to review critically the available data of functional as well as radiographic outcome.

With the advent of new hip implants (resurfacing and short stem prosthese) current treatment recommendations have to be reevaluated. The indication for surgical treatment in hip osteoarthritis as well as the choice of implants is mainly based on personal experience of the surgeoun (internal evidence) and clinical data (external evidence). Experimental studies can support the information from clinical trials and are necessary to evaluate the mechanical properties of an implant. They do not replace the clinical evaluation, however.

The level of evidence depends on type, quality and quantity of available data from published investigations. Recent innovations like surface replacement and short stem prostheses have mainly been investigated in single center observational studies with a relatively short followup.

Wider introduction of new implants, however, needs continuous evaluation of clinical and radiographic performance. Examples are given, how this monitoring should be performed in a clinical setting.

Appropriate clinical studies that address the efficacy and effectiveness of orthotic treatment in general are difficult to identify, particularly in postoperative treatment of congenital clubfeet. Clinical experience, however, seems to necessitate casting and splinting for a certain time after surgical correction to prevent relapses.

Although treatment recommendations range from three months to two years after surgery, duration and intensity of orthotic therapy may depend on the severity of the clubfoot deformity, underlying disorders and the surgeon’s experience.

Knee-ankle-foot orthoses with a knee flexion of 90 are most commonly prescribed after the removal of postoperative casts. They allow appropriate abduction of the foot, and daily stretching exercises that can be performed by the parents in combination with physical therapy. Most splints are made of polyethylene or polypropylene, and current designs include static or rigid ankle and forefeet.

Some authors also recommend significantly smaller orthoses that are used in metatarsus varus treatment: Denis-Browne bars and orthoses with locking or elastic swivel joints that allow the hindfoot and forefoot components to be adjusted in relation to each other. However, since they do not have a moulded heal, they tend to slip off and cannot prevent recurrence of the equinus. Their application is also restricted to pre-walking infants unless considered for use at night.

Outflare shoes (anti-varus shoes) also keep the forefoot in the “corrected position”. To obtain a necessary 3-point correction, however, certain construction principles are mandatory. The hindfoot must be kept in high heel cup and the first metatarsal is pushed laterally against the counter-pressure that is exerted on the cuboid by the most distal and lateral part of the heel cup.

After introduction of continuous passive motion (CPM) into the treatment of congenital clubfeet, some groups have published encouraging results. Although the advocates of this treatment state that the duration of plaster cast immobilisation can be shortened after surgery, further evaluation of outcome and cost-effectiveness of this approach is necessary.