Aims

The aim of this retrospective study was to compare the correction achieved using a convex pedicle screw technique and a low implant density achieved using periapical concave-sided screws and a high implant density. We hypothesized that there would be no difference in outcome between the two techniques.

In recent years, the direct anterior approach (DAA) has become a standard approach for primary total hip arthroplasty (THA). With the increasing use of the DAA in primary cases also more and more revision surgeries are performed through the same interval. With ability to extend the DAA interval proximally and distally, loose cups, loose stems, and even periprosthetic femoral fractures (PPF) can be treated. Especially, PPF are devastating complications causing functional limitations and increased mortality. Therefore, we conducted a study to report the outcome of surgical treatment of PPF with the DAA interval.

We report on the one year complications and mortality in 40 cases with a mean clinical follow-up of 1.5 years. Mean age of patients was 74.3 years. Fractures were classified as Vancouver B2 (36), and B3 (N=4). In 14 cases, a standard stem was used, and in 26 cases a modular revision stem. In 30 cases, a distal extension +/- tensor release was used, in 4 cases a proximal tensor release was done, and in the remaining 6 cases revision could be performed without extension of the approach.

Median cut/suture time was 152 minutes (IQR 80 – 279). The overall complication rate in our patient group was 12.5%. 2 patients died in the first three months after operation. One patient had a transient femoral nerve palsy, which completely recovered.

The DAA interval to the hip for the treatment of PFF showed similar results compared with other approaches regarding mortality, complications, fracture healing, dislocation rate and clinical results. We conclude that femoral revision in case of PPF in the DAA interval is a safe and reliable procedure. Each Vancouver type of periprosthetic fracture can be treated by use of this approach.

We aimed to investigate the clinical consequences of intraoperative acetabular fractures. Between 2003 and 2012, a total of 3391 cementless total hip arthroplasties (THA) were performed at the Dept. of Orthopaedics, Innsbruck Medical University. Of those, a total of 160 patients underwent a CT scan within 30 days postoperatively. The scans of 44 patients were not suitable for analyse due to thick scan layers. Of the remaining 116 patients, 76 had a fracture. Reasons for CT-scans were suspected bleeding, hip pain, abdominal symptoms, etc.

The fractures included 59 isolated acetabular fractures, the rest of fractures was in the superior or inferior pubic ramus or the tuber ischiadicum.

Four cases out of the 59 acetabular fractures underwent revision surgery due to periprosthetic joint infection after 0, 2, 10 and 23 months. Four patients underwent revision due to cup loosening after 13 and 14 days as well as after 16 and 24 months. Of those, three showed a central acetabular fracture with protrusion.

In 33 of the remaining 51 patients, a minimum of 3 x-rays was available for migration analysis with EBRA. In 6 patients, the x-rays were not comparable to each other. The 27 remaining acetabular fractures were categorised according to AO classification in 62A1 (1; posterior wall), 62A2 (16; posterior column), 62A3 (6; anterior wall), and others (4). Four hips showed initial migration of more than 3 mm in the first 6 months. One had a central fracture, and was lost for follow-up after 8 months. Two had an anterior column fracture and showed no further migration after 6 months. One showed also a radiolucency of more than 2 mm in all 3 zones and was lost for follow-up.

We conclude that intraoperative acetabular fractures occur more often than we expected. Fractures of the acetabular ring involving one column do not seem to compromise the long-term stability of the implant. Central fractures required revision or showed loosening proved by high cup migration.

Introduction

Austin Moore cervicocephalic prostheses have been a therapeutical option for femoral neck fractures in patients with a reduced general condition for many years. Since treatments other than total hip arthroplasties have also been included in National arthroplasty registers during the last decade, adequate reference data for comparative analyses have recently become available.

Introduction

End-stage ankle osteoarthritis is a debilitating condition that results in functional limitations and a poor quality of life. Ankle arthrodesis (AAD) and total ankle replacement (TAR) are the major surgical treatment options for ankle arthritis. The purpose of the present study was to compare preoperative and postoperative participation in sports and recreational activities, assesses levels of habitual physical activity, functional outcome and satisfaction of patients who underwent eighter AAD or TAR.

Between 1978 and 1997 all newborns in the Austrian province of Tyrol were reviewed regarding hip dysplasia and related surgery. This involved a mean of 8257 births per year (7766 to 8858). Two observation periods were determined: 1978 to 1982 (clinical examination alone) and 1993 to 1997 (clinical examination and universal ultrasound screening). A retrospective analysis compared the number and cost of interventions due to hip dysplasia in three patient age groups: A, 0 to < 1.5 years; B, ≥ 1.5 to < 15 years; and C, ≥ 15 to < 35 years.

In group A, there was a decrease in hip reductions from a mean of 25.2 (sd 2.8) to 7.0 (sd 1.4) cases per year. In group B, operative procedures decreased from a mean of 17.8 (sd 3.5) to 2.6 (sd 1.3) per year. There was a 75.9% decrease in the total number of interventions for groups A and B.

An increase of €57 000 in the overall cost per year for the second period (1993 to 1997) was seen, mainly due to the screening programme. However, there was a marked reduction in costs of all surgical and non-surgical treatments for dysplastic hips from €410 000 (1978 to 1982) to €117 000 (1993 to 1997). We believe the small proportional increase in costs of the universal ultrasound screening programme is justifiable as it was associated with a reduction in the number of non-surgical and surgical interventions. We therefore recommend universal hip ultrasound screening for neonates.

Background: The chevron osteotomy is a widely accepted method for the correction of mild to moderate hallux valgus deformity that reveals good to excellent results in terms of radiographic correction of hallux valgus deformity as well as functional outcome scores. However, recent pedobarographic studies have shown that there is decreased load of the big toe region and the first metatarsal head region respectively at a short and intermediate-term follow-up Sufficient load of these structures is essential in order to provide physiological gait patterns. The purpose of the present study was to determine if a modification in the postoperative regimen improves the functional outcome of chevron osteotomy for correction of hallux valgus deformity.

Methods: 29 patients with an mean age of 58 years who suffered on mild to moderate Hallux valgus deformity without radiographic signs of osteoarthritis of the first MTP joint who underwent chevron osteotomy were included in this prospective study. Postoperatively patients were placed in a forefoot relief shoe for 4 weeks. After this period they received a multimodal rehabilitation program including kryotherapy, lymphatic drainage, mobilisation, manual therapy, strnthening exercises and gait training. The patients received a mean of 4.2 treatment sessions and the sessions took place one time a week for 3 to 6 weeks. Preoperatively and one year after surgery plantar pressure distribution parameters including maximum force, contact area and force-time integral were evaluated. Additionly the AOFAS score, ROM of the first MTP and plain radiographs were assessed. The results were compared using Student’s t-test and level of significane was set at p< 0.05.

Results: In the big toe region maximum force increased from 72.2 N presurgically to 106.8 N at one year after surgery, contact area increased from 7.6 cm2 preoperatively to 8.9 cm2 one year postsurgically and force-time integral increased from 20.8 N*sec to 30.5 N*sec. All changes were statistically significant.(p< 0.05) For the first metatarsal head region maximum force increased from 122.5 N presurgically to 144.7 N one year after surgery and force-time integral increased from 42.3 N*sec preoperatively to 52.6 N*sec one year postoperatively. However, those changes were not statistically significant. (p=0.068; p=0.055)The mean AOFAS score increased from 61 points preoperatively to 94 points at follow-up (p< 0.001). The average hallux valgus angle decreased from 31° to 9° and the average first intermetatarsal angle decreased from 14° to 6° respectively.(p< 0.001)

Conclusions: The results of the present study indicate that postoperative physical therapy and gait training help to improve weight-bearing of the big toe and first ray respectively. Therefore, there is a restoration of physiological gait patterns in patients who recieve this postoperative regimen.

Study Design: A prospective study evaluated patients’, orthopaedists’ and not affected children of the same age ratings’ of preoperative and postoperative cosmesis in adolescents undergoing posterior spinal fusion for idiopathic scoliosis. The cosmetic result based on a questionnaire was compared to clinical and radiological parameters. There was no correlation between the SAQ and objective clinical and radiologic parameters at all, whereas clinical and radiological parameters showed good correlation. We recommend to standardly evaluate the cosmetic outcome as after scoliosis correction surgery.

Introduction: Improving cosmesis is an important goal in scoliosis surgery. Patients’ satisfaction with the cosmetic outcome is essential in their evaluation of the surgical result. However, only few efforts were made in the past to investigate the cosmetic outcome. We performed a a prospective study evaluated patients’, orthopaedists’ and not affected children of the same age ratings’ of preoperative and postoperative cosmesis in adolescents undergoing posterior spinal fusion for idiopathic scoliosis. The cosmetic result based on a standardized questionnaire (SAQ, spinal appearance questionnaire) was compared to clinical and radiological parameters.

Patient sample: Preoperative and postoperative photographs were taken from 32 patients (22 female, 10 male, average age 14.6 years) preoperatively and postoperatively in a standardized manner.

Materials: The photographs were assessed by use of a modified SAQ. In addition radiological measurements were performed like the cobb angles of the main curves in the coronal and sagittal plane, plumb line deviation, shoulder inequality and pelvic obliquity. The clinical investigation included the measurements of shoulder asymmetry, pelvic obliquity, rip and lumbar hump, plumb line deviation, breast asymmetry and the postoperative evaluation of the scar.

Results: The items general appearance, body shape, rib hump, and shoulder inequality of the SAQ improved most (p< 0.025). The patients judged the cosmetic result better than surgeons and healthy children (on average: 11 out 15 parameters of the SAQ improved) The surgeons came to the worst judgement (only 5 of 15 parameters improved). The interrater correlation of the surgeons was poor (ICC< 0.58). There was no correlation between the SAQ and objective clinical and radiologic parameters at all, whereas clinical and radiological parameters showed good correlation.

Conclusion: As shown in our results objective clinical and radiological parameters do not correlate with the evaluation of the cosmetic result. Therefore we recommend to establish the evaluation of the cosmetic outcome as standard investigation after scoliosis correction surgery.

Objective: The aim of this study was to show the effect of a universal (all neonates) ultrasound screening in newborns on the incidence of operative treatment of hip dysplasia.

Materials: A retrospective study was performed and all newborns of the county Tyrol (Austria) between 1978 and 1998 (8257 births / year ((range: 7766 – 8858)) were reviewed regarding hip dysplasia and following hip surgeries. Between 1978 and 1983 clinical examination alone was performed to detect hip dysplasia. Between 1983 and 1988 an ultrasound screening programme according to Graf was initiated in our county. Between 1988 and 1998 ultrasound screening was performed in all newborns. Hence two observation periods were determined: 1978–1983 and 1993–1998. The time period between 1983 and 1993 was excluded to minimize bias and learning curve regarding the initiation of the ultrasound screening programme. A retrospective comparative analysis of the two observation periods regarding surgical treatment and costs caused by hip dysplasia was performed. During the observation period indication for surgery did not change, however new treatment techniques were introduced. Patients with neuromuscular and Perthes diseases were excluded. According to age dependent surgical procedures three patient samples were determined: Group A: 0–1.5 years, Group B: 1.5–15 years and Group C: 15–35 years.

Results: Comparison of the two observation periods showed no influence on the number of interventions for dysplastic hips in group C (pelvic osteotomies and VDROs). In group A, a decrease of hip reductions was seen from 25.6±3.2 to 7.0± 1.4 cases per year. In group B, there was a decrease of operative procedures for dysplastic hips from 18.0±3.2 to 3.4±1.3 interventions per year. Since the introduction of universal hip ultrasound screening the decrease of the total number of interventions for all groups was 78.6%. Comparison of costs of the two observation periods showed an increase of all costs caused by DDH and CDH of 57.000 euro/ year for the time period between 1993 and 1998 which was mainly caused by the ultrasound screening programme. There was a significant reduction of costs regarding operative and non operative treatment for dysplastic hips from 410.000 euro (1978–1983) to 117.00 euro (1993–1998).

Conclusion: Initially there were higher costs caused by the screening method, but on the other hand total number and costs for operative and nonoperative treatment of dysplastic hips were significantly reduced by the universal ultrasound screening programme. In our mind patient’s and family distress and pain related to interventions performed for CDH and DDH justify the slight increase of costs caused by the universal screening programme. We therefore recommend universal hip ultrasound screening for neonates.

Background: Implant fractures are complications that have a great impact on the patient’s quality of life after total hip arthroplasty. Nevertheless their occurrence is often considered as rare in clinical practice. We compared incidences of implant fractures in various datasets in order to calculate the risk of a fracture and assess the quality of these datasets for such evaluations.

Methods: In a structured literature analysis based on a standardised methodology the incidence of reoperations was evaluated comparing clinical studies published in Medline-listed journals and annual reports of National Arthroplasty Registers worldwide. Case reports and experimental studies were not considered.

Results: The majority of clinical studies are monocentre trials. The publications comprise a cumulative number of 72,571 stems with 234 stem fractures, 73,743 cups with 191 component fractures, and 16,381 ceramic heads with 44 fractures. A survey among the members of the American Association of Hip and Knee Surgeons covered 64,483 primary operations, hence including a similar number of primary cases as all monocentre studies together. This dataset involves 355 implant fractures.

By contrast, worldwide Register data refer to 733,000 primary operations, i.e. approximately 10 times as many as sample-based datasets.

In general, sample-based datasets present higher revision rates than register data. The deviations are high, with a maximum factor of 64 for hip stems. Whereas the AAHKS survey exhibits lower deviations than the monocentre trials, they are still too high for this data collection tool being considered as reliable and safe to provide valid data for general conclusions.

The incidence of implant fractures after total hip arthroplasty in pooled worldwide arthroplasty register datasets is 304 fractures per 100.000 implants. In other words, one out of 323 patients has to undergo revision surgery due to an implant fracture after THA in their lifetime.

Conclusion: For general assessments in the context of implant fractures, register data have the highest value. Clinical studies, which often focus on a particular implant, are of very limited value for global conclusions. Structured surveys produce more reliable data than clinical studies and are superior to monocentre trials. However, the AAHKS survey presents data that also show considerable differences to data from registers.

For the detection of rare, but severe complications like implant fractures sample-based studies achieve the goal of providing accurate figures only to a very limited extent, even if the samples are large. Here, too, comprehensive national arthroplasty registers are the most suitable tool to identify such incidents and calculate reliable figures.

Contrary to the prevalent opinion, implant fractures still are a relevant problem in arthroplasty.

Background: Within the scope of the EU project EUPHORIC a methodology for direct comparison of different datasets was developed and applied on a sample of implants, among them the Oxford Unicompartmental Knee Arthroplasty (Oxford Uni). The aim was to identify potential bias factors inherent in the datasets and evaluate the outcome achieved with this implant.

Materials and Methods: A structured comparison was performed of data published on the revision rate of the Oxford Unicompartmental prosthesis. Both clinical follow-up studies published in Medline-listed journals and worldwide Register data were included. The data were stratified with regard to potential influence factors like the individual research groups or the geographical origin of the papers.

Results: A major proportion of the published data, between 50 and 75%, depending on the method of calculation, comes from studies including the developing institution in Oxford. The results published by this group deviates statistically significantly from the reference datasets from Register data or independent research groups. Data from the developing hospital show mean revision rates that are 4.4 times lower than those based on worldwide Register data, and 2.74 times lower than in independent studies. As opposed to this, independent studies on average publish data that are reproducible in Register data.

Conclusion: A conventional meta-analysis of clinical studies is significantly affected through the influence of the developing institution and is therefore subject to a bias. Neither through arthroplasty Register outcome data nor by other research groups that have disclosed outcome information on the Oxford Uni can the excellent results be reproduced that were published by the inventors.

Compared to other implants for unicompartmental knee arthroplasty in worldwide arthroplasty Registers, the Oxford Uni shows good results.

For the assessment of the outcome of implants, register data are to be rated superior and, in terms of reference data for the detection of potential bias factors in the clinical literature, can provide an essential contribution for scientific meta-analyses.

Background: Adjuvant radiotherapy has shown to improve local control in patients with soft tissue sarcoma. Additional brachytherapy represents a means of enhancing the therapeutic ratio, as biological and dosimetric advantage over single external-beam irradiation (EBRT) can be expected. High-dose-rate intraoperative brachytherapy (IOHDR) as a boost therapy should be able to further diminish the rate of local recurrence even when performing marginal resection.

Patients and Methods: Within a period of 10 years, we prospectively studied 84 adult patients treated by marginal resection, IOHDR using the flab technique and EBRT for soft tissue sarcomas. There were 67 high-grade and 17 low-grade tumors, 70 were > 5 cm. Mean follow-up was 37.2 months (range 1–121 months).

Results: There were two local recurrences, following further resection one patient is without evidence of tumor. No treatment-related loss of limb or life occurred. All patients maintained functioning extremities as evidenced by a mean Musculoskeletal Tumor Society (MSTS) functional score of 89.1 (43–100). Treatment-related wound morbidity occurred in a fifth of all patients, as consequence of revision surgery one patient sustained neurovascular complications. The 5-year actuarial disease-free survival was 81.6%. Meta-static disease developed in eighteen patients, all of them had died at last follow-up. There were four cases of late radiation related complications (two fractures of the femur due to radiation osteonecrosis and two late palsies of ischial nerve).

Conclusions: IOHDR using the flab technique in combination with EBRT and marginal resection is an efficient treatment technique leading to excellent local control rates and limited functional impairment.

Background: Recently, the effects of radiculopathy and nerve root blocks on driving reaction time (DRT) have been presented in the literature. To our knowledge, the relation between lumbar spinal fusion and DRT has not been studied before, although important for driving safety. So, we conducted the current study to test the hypotheses that DRT in the context of lumbar fusion is 1) altered in pre-postoperative comparison, 2) influenced by pain, 3) influenced by the patient’s driving skill and 4) different to the DRT of healthy controls.

Methods: 21 consecutive patients (age 53.5 years, SD 10.8) receiving primary lumbar fusion were tested for their DRT 1 day preoperatively (pre-op), 1 week postoperatively at the day before discharge (post-op) and at 3 months (follow-up; FU). DRT was assessed with a custom made driving simulator. Additionally, also the level of back pain was determined by VAS for usual pain (VAS-U) and for pain during testing (VAS-T). We also collected the participants’ subjective driving frequency. We used normative DRT data from 31 healthy controls of similar age for comparison with the patients.

Results: Pre-op DRT was 685 msec (Md; IQR 246), post-op DRT increased to 728 msec (Md; IQR 264) and decreased again to 671 msec (Md; IQR 202) at FU (p=0.007). Post-hoc analyses (alpha=0.017) found significant differences between post-op and FU DRT (p=0.007). Moderate to high correlations (between 0.537 and 0.680) were found between VAS of back pain and DRT (p between 0.001 and 0.012). No correlations were found between driving frequency and DRT. Controls showed a DRT of 487 msec (Md; IQR 116) which was significantly different from DRT of the patients at all three test occasions (p< 0.001).

Conclusion: We found minor increase in DRT 1 week post-op followed by a definite and significant decrease at 3 months FU. We think it is safe – with respect to DRT - to resume driving 3 months after lumbar fusion. It is difficult to draw any conclusions about the period between discharge and 3 months. We also found moderate and high correlations between DRT and the level of back pain and assume that back pain is a relevant factor influencing DRT.

Introduction: Clinical follow-up studies are sample based, in contrast to arthroplasty register data, which refer to the entire population treated. Aim of this study is to assess the differences in revision rate to quantify bias-factors in published literature.

Materials and Methods: A structured literature review of Medline-listed peer reviewed journals concerning the STAR Total Ankle Replacement have been conducted.

The published results from clinical follow up studies have been compared to Arthroplasty register Results: Results: 24% of all papers were published by the inventor of the implant.

These publications show a 3,4 times lower revision rate compared to independent studies and a 4,6 times lower revision rate compared to Register based publications.

The cumulative revision rate per 100 observed component years of register based publications is 1,36 times higher compared to independent clinical studies. The difference is statistically not significant.

Pooling the published data from all follow up studies the impact of the studies published by the inventor leads to a statistically significant bias.

Discussion and Conclusion: Publications by the inventor of the implant are overrepresented in peer reviewed scientific journals. This bias has a statistically significant impact on the final result of a Metaanalyses.

Arthroplasty Register data are able to detect bias factors and lead to a better quality of assessments concerning the outcome of arthroplasty.

Background: The role of frontal plane tibiofemoral alignment in subjects with patellofemoral pain syndrome (PFPS) is controversial and rarely discussed in the literature. As well, little research has been done on the effects of the hamstrings muscles on PFPS. The aim of the current study was to determine whether, in individuals with PFPS, frontal plane tibiofemoral alignment or muscular activity of the index knee’s crossing muscles is altered during maximum eccentric leg press exercise.

Methods: This cross-sectional study involved 19 patients with PFPS and 19 control subjects who were matched according to gender, age, and physical activity. During eccentric leg press action, frontal plane tibiofemoral alignment was assessed with a motion analysis system based on skin markers. Simultaneously, surfaceelectro-myography was used to assess the activity levels of the relevant knee crossing muscles. To assess the activity under functional conditions, a leg press with a footplate having variable stability was used for barefoot testing.

Findings: The PFPS subjects did not have significantly different frontal plane leg alignment compared to controls. On electromyography (EMG), PFPS patients had significantly lower levels of hamstring activity during eccentric leg exercise. The differences between the 2 groups (%; absolute differences normalized EMG) ranged from 19.57% (semitendinosus; stable footplate; p = 0.017) to 20.04% (biceps femoris; unstable foot-plate; p = 0.019) and 32.03% (semitendinosus; unstable footplate; p = 0.002).

Interpretation: PFPS is not linked to altered frontal plane leg alignment during eccentric leg pressing. However, PFPS is associated with eccentric under-activation of the hamstrings, which may be a compensatory strategy that maintains patellofemoral joint pressure within bearable levels.

Background: Clinical scores are widely used to evaluate the outcome of total knee arthroplasty (TKA). However, a lack of uniformity, the use of different terminology, and the diversity of methods used to translate numerical data into clinical outcomes have been described as potential problems. Gait analysis is believed to provide more objective parameters and allow the ascertainment of functional performance after knee arthroplasty. The aim of the present study was to obtain information about the correlation between the outcome in terms of locomotion and the clinical knee score after TKA.

Methods: 29 consecutive patients waiting for total knee arthroplasty (TKA) were included in the study. The Hospital for Special Surgery Score (HSS), the Knee Society Score (KSS) and a gait analysis were conducted 1 day prior to surgery and 3 months postoperatively. The following kinematic and temporospatial gait parameters, whose relevance has been established in knee arthroplasty were analyzed: In the sagittal plane, the following variables were determined: maximum knee flexion stance, maximum knee flexion swing, minimum hip flexion (= maximum hip extension) and minimum ankle dorsiflexion (= maximum ankle plantarflexion). The maximum pelvic obliquity stance was determined for analysis in the frontal plane while stride length, double support and gait velocity were calculated for temporospatial analysis. Data from the KSS and HSS were analyzed for the subgroups named pain, knee (knee-specific parameter), function and total sum. Pearson’s correlation coefficients were calculated for the above mentioned gait parameters and for knee score subgroups pre–and postoperatively.

Results: Preoperatively, positive correlations of r > 0.5 (0.001 < p < 0.005) were ascertained for maximum knee flexion swing, maximum pelvic obliquity stance, gait velocity and stride length, and were mainly determined for the subscore of function and the total sum of KSS and HSS. A lower correlation (r = 0.388, p = 0.041) was determined for maximum knee flexion stance. Postoperatively, positive correlations of r > 0.5 (0.000 < p < 0.003) were determined for gait velocity, maximum pelvic obliquity stance and stride length, mainly for the subscore of function and the total sum of KSS and HSS. A negative correlation of r < −0.5 (0.001 < p < 0.009) between these score subgroups and double support was only ascertained postoperatively. No correlations were registered between pain subscores of KSS or HSS and any of the gait variables.

Interpretation: In the current study we established high correlations particularly between temporospatial parameters and functional and total scores of KSS and HSS pre-and postoperatively. It is concluded that the functional subscores of KSS and HSS are particularly suitable to assess the dynamic outcome of TKA.

High tensile stress has been considered as a contributing factor to the rim fracture of polyethylene acetabular cup liner. We performed the 3 D Finite Element Analysis (FEA) to compare the stress patterns at the polyethylene liner rim as a function of polyethylene thicknesses and whether or not rim was supported by the titanium acetabular shell extension. Two 3.1 mm thick generic 52 mm titanium alloy acetabular shells with and without 2 mm high rim support extension were modelled. Six corresponding Ultra High Molecular Weight Polyethylene (UHMWPE) liners with inner bearing diameters ranging from 22 mm to 44 mm and same outer diameters, were fixed in the shells. A 2 450 N load was applied through the corresponding CoCr femoral heads to the rims of liners while the acetabular shells were fixed on the outer spherical surface. The FEA was performed in half body of the assembly. The maximum principal stresses at the rim regions of UHMWPE liners were recorded.

The results showed that in all rim supported conditions, the maximum principal stress were in compressive patterns, a preferred pattern to reduce the potential polyethylene liner fracture. In rim unsupported conditions, the stresses was in tensile on the internal bearing surface when polyethylene liner thickness was bellow 5 mm, or was bellow 9 mm if the average maximum principal stress cross the rim was considered.

We conclude that the metal rim support changes the stress pattern in the rim region of UHMWPE liner to compressive for all liner thicknesses. The stress pattern turns to tensile, or there will be a higher potential for rim fracture, if UHMWPE liner is unsupported and the polyethylene rim thickness is less than 9 mm.

Although components used this study did not include the locking details which add higher stress concentrations, the trend of stress patterns should follow the results found in this study.

Background and purpose: Implantation of the femoral component at 10 to 15 degrees of anteversion is recommended in total hip arthroplasty. Surgical guidelines suggest that the lower leg be positioned horizontally or vertically with the knee flexed to 90° (figure of four). By constructing a perpendicular axis (a “figure-of-four” axis) to the lower leg, anteversion of the stem is approximated. This study was performed to validate the figure-of-four axis as a reliable intraoperative tool to approximate the retrocondylar line as reference for stem version.

Method: In 21 cadavers placed supine on an operating table, the lower legs were aligned to the horizontal plane. Using a box column drill, Steinmann nails were inserted perpendicular to the lower leg into the medial epicondyles. The Steinmann nails were replaced by cannulated titanium screws, representing the figure-of-four axis. The femoral neck axes, retrocondylar lines and the figure-of-four axes were determined using CT images of the specimen.

Results: The median version of the femoral neck axis was anteversion of 9.8° (IQR 4.5°–15.1°). The median figure-of-four axis showed a deviation of 0.5° (IQR −2.1°−2°) in relation to the retrocondylar line, whereas the median difference of the axis in relation to the femoral neck axis was 9.5° (IQR −13.6° – −2.1°).

Interpretation: The figure-of-four axis, being nearly parallel to the retrocondylar line, is a valid indirect method to determine stem version intraoperatively in patients without varus/valgus deviations of the knee.

Introduction: Minimally invasive total hip arthroplasty has evoked substantial controversy with regard to whether it provides superior outcomes compared with conventional total hip arthroplasty. The objective of this study was to compare the results of a minimal invasive direct anterior approach (MIDA) with those of a conventional lateral transgluteal approach (CLT).

Methods: 120 patients (120 hips) admitted for unilateral total hip arthroplasty were randomized to undergo surgery via minimal invasive direct anterior or conventional lateral transgluteal approach. Patients with a body mass index of more than 35, previous hip surgery, preoperative neurological deficits and with an age of more than 80 years were excluded. Two surgeons performed all procedures. To estimate muscle damage serum creatinkinase was assessed. Blood loss was calculated according to Rosencher by comparing preoperative to postoperative hematocrit. Postoperative pain and the ability to perform the activities of daily living were recorded in a dairy via modified WOMAC first on a daily basis, then on each second day and finally once a week for a total of 12 weeks. WOMAC questionnaire and SF-36 were administered at 6 weeks and 3 months follow-up.

Results: The groups were similar demographically. Patients in MIDA group had significantly less total blood loss (p = 0.006), postoperative blood levels of creatinine kinase were significantly lower (p = 0.001). Operative time was similar in both groups, we found no difference in component placement. Physical component summary of SF-36 at 12 weeks follow-up showed a significant benefit for the MIDA group. Averaged modified WOMAC scores and their pain and function subscores demonstrated a clear advantage on every recorded day during the first 12 weeks for MIDA. Median WOMAC sum score and respective pain as well as function subscores were better in the MIDA group at 6 and 12 weeks follow up.

Conclusions: A minimally invasive direct anterior approach is superior to a conventional lateral transgluteal approach with regard to blood loss and muscle trauma, resulting in better health related quality of life in the first three months after operation.

Study Design/Objective: Prospective two-leg cohort study on anterior cervical fusion versus cervical arthroplasty with emphasis on clinical outcome measures.

Patients and Methods: Between August 2003 and May 2005 21 consecutive patients underwent anterior cervical fusion with or without anterior decompression with 26 levels fused. Between December 2004 and August 2006 24 patients had cervical arthroplasty with 30 levels replaced. The mean age at operation of the fusion group was 52 years and 5 months (46–69) and for the arthroplasty group 51 years and 2 months (42–62). To establish fusion the Cervios® cage (Synthes) with or without anterior plating was used. In the arthroplasty group the Prodisc C® disc prothesis (Synthes) was used. Contraindication for arthroplasty were osteoporosis, osteopathies, spinal canal stenosis, hypertrophic spondylarthrosis, spondylolisthesis, tumors and privious infection. Both groups were comparable with respect to age and gender, diagnosis, level distribution and preoperative clinical outcome measures (VAS for nack pain and arm pain, neck disability index and SF-36–sub-scores pain, function, vitality).

Results: Postoperatively all of the clinical outcome measures significantly improved in both groups. After three months postoperatively no significant further improvement was evident.

VAS neck pain: Fusion group/arthroplasty group: Preoperatively 6.2/5.9 n.s., 6 weeks 3.5/3.1 n.s., 12 weeks 2.1/1.9 n.s, 1 year 2/2.1 n.s.

In the fusion group we had 1 recurrent radiculopathy and 1 non union without the need of further intervention. In the arthroplasty group we faced 1 recurrent laryngeus recurrens nerve palsy and 3 spontaneus fusions within 1 year postoperatively, which might not be classified as complication.

Conclusion: Short term outcome after both procedures is excellent in terms of pain relief and function. 10% spontaneus fusion after disc replacement within the first year was evident. In our series we found better results after 3 months to 1 year postoperatively with respect to the neck disability index and SF-36 subscore pain within the arthroplasty group.