Martin Thaler

Revision rates after total joint replacement: CUMULATIVE RESULTS FROM WORLDWIDE JOINT REGISTER DATASETS

In a systematic review, reports from national registers and clinical studies were identified and analysed with respect to revision rates after joint replacement, which were calculated as revisions per 100 observed component years. After primary hip replacement, a mean of 1.29 revisions per 100 observed component years was seen. The results after primary total knee replacement are 1.26 revisions per 100 observed component years, and 1.53 after medial unicompartmental replacement. After total ankle replacement a mean of 3.29 revisions per 100 observed component years was seen. The outcomes of total hip and knee replacement are almost identical. Revision rates of about 6% after five years and 12% after ten years are to be expected.

Cost-effectiveness of universal ultrasound screening compared with clinical examination alone in the diagnosis and treatment of neonatal hip dysplasia in Austria

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.

Reduced variability in cup positioning: the direct anterior surgical approach using navigation

Background and purpose Correct positioning of the acetabular component is important in total hip arthroplasty (THA). We evaluated the effect of an imageless navigation system on the accuracy of cup positioning using a minimally invasive direct anterior approach. Methods Hip replacements were performed in 44 cadaveric hips (22 cadavers) that were divided randomly into 2 groups. In the study group, THA was performed using an imageless navigation system. In the control group, no navigation system was used. CT scans were taken postoperatively. Using 3D reconstructions, the cup position was determined in relation to the frontal pelvic plane. The goal was to place each cup at 45° of inclination and 20° of anteversion, as recommended by the manufacturer. Results In the navigated group, there was a statistically significantly smaller range of deviation from the target angles of inclination and anteversion relative to the control group. Interpretation We conclude that imageless navigation improves the accuracy of cup placement in minimally invasive THA using the direct anterior approach.

Outcome of the cementless Taperloc stem: a comprehensive literature review including arthroplasty register data

Background and purpose The validity of various data sources for the assessment of the outcome quality of medical devices was investigated by comparative analysis of the published data sources available for a sample of implants. It was the aim of the study to determine the performance of this implant and to identify potential bias factors inherent to the various datasets. Methods A comprehensive literature search was carried out from English-language, peer-reviewed journals and worldwide reports from national arthroplasty registers. Publications from Medline-listed journals were included. The main parameter was revision rate, calculated as “revisions per 100 observed component years” to allow adjusted direct comparison of different datasets. Results Of 16 clinical studies that met the inclusion criteria, 9 originated from the implant developers hospital. In the clinical studies category, publications from the developers hospital suggested considerably lower revision rates than the other datasets. In fact, the values quoted were 5.5 times below the average of all other studies, and 9.51 times lower than in the Australian arthroplasty register. These differences are statistically significant. Interpretation The cementless Taperloc stem is an implant that shows good performance regarding revision rates in registry data and in clinical studies. However, the excellent results published by the developers clinic are generally not reproducible by other surgeons. In terms of reference data, registry data are able to make an important contribution to the assessment of clinical sample-based studies, particularly regarding evaluation of the extent to which published results are reproducible in daily routine.

Restoration and preservation of disc height and segmental lordosis with circumferential lumbar fusion: a retrospective analysis of cage versus bone graft.

Study Design Retrospective radiographic analysis. Objective To determine whether restoration and preservation of (a) disc height and (b) segmental lordosis differ between patients treated with circumferential lumbar fusion using a bone graft or a cage for anterior support. Summary of Background Data Restoration of disc height and lordosis is considered to be of crucial importance in circumferential fusion (CF). To determine whether restoration and preservation of disc height and segmental lordosis are dependent on the type of anterior support used, we compared the use of a cage with that of a bone graft in CF. Methods We retrospectively analyzed disc height and segmental lordosis in patients treated with primary lumbar monosegmental CF. The minimum period of follow-up was 9 months. A cage was used for anterior support in 23 patients and a bone graft in a further 23 patients. Disc height was determined on radiographs using an earlier introduced and validated distortion-compensated roentgen analysis, which was developed to compensate for distortion in central projection, off-center position, variation of stature, axial rotation, and lateral tilt of the spine. Results Disc height was restored in both groups but differences between preoperative and postoperative disc heights were significantly greater in the cage group (P=0.006). The cage also proved to be superior with regard to disc height preservation after follow-up (P=0.001). In addition, there was significantly less postoperative loss of segmental lordosis in the cage group (P=0.026). Conclusions The cage proved superior to the bone graft as anterior support in CF with respect to restoration/preservation of lordosis and disc height. However, no conclusions concerning clinical outcome or cost effectiveness can be drawn on the basis of this study.

Correlation between radiographic assessment and quality of life after total knee arthroplasty

The correlation between radiographic and clinical outcome was investigated for total knee arthroplasty. One hundred three total knee arthroplasties in 98 patients were investigated at an average follow-up of 10.8 years (range, 2-17 years). For radiographic evaluation the Radiographic Evaluation System of the Knee Society was used. For assessment of clinical outcome four disease-specific scores, and the Nottingham Health Profile were applied. A significant correlation was found between the extent of radiolucent lines of the tibial component and the Nottingham Health Profile (correlation coefficient: 0.61, p<0.0001). For the disease-specific scores the correlation was low (correlation coefficient: 0.30-0.50). For the prosthetic alignment no significant correlation was found (p<0.05). The current results show that a correlation was found between radiological assessment and several clinical scores. We suggest that a quality-of-life score should be included in the follow-up evaluation of total knee arthroplasty.

Injury of the right and left inferior epigastric artery during the implantation of a stand-alone ALIF cage through a left retroperitoneal approach: a case report

Various perioperative vascular complications of anterior lumbar spine procedures have been described in orthopaedic literature. We report the unusual case of a perioperative bleeding from the right and left epigastric inferior artery occurring when using a stand-alone ALIF device (Synfix, Synthes, Oberdorf, Switzerland) at the L5/S1 level through an anterior left retroperitoneal approach. The primary stability of the Synfix is achieved by four divergent screws which are inserted through the anteriorly located plate into the neighbouring vertebral endplates. For the screw insertion the surrounding structures have to be mobilized more extensively than during a “standard” anterior lumbar interbody fusion (ALIF) procedure. The epigastric inferior arteries were embolized by applying polyvinyl alcohol particles and metal coils. The retroperitoneal haematoma caused herniation of the external rectus sheath. Hence revision surgery with removal of the haematoma and resuturing of the rectus sheath were performed. Insertion of divergent screws of the Synfix device may cause severe distension and rupture of the epigastric vessels. This case shows that a lesion of the right epigastric artery may be a hazard even in left retroperitoneal approaches. To the author’s knowledge this is the first case describing a lesion of the right epigastric artery during an ALIF procedure through a left retroperitoneal approach.

Comparative pooled survival and revision rate of Austin-Moore hip arthroplasty in published literature and arthroplasty register data.

The aim was to evaluate the pooled survival and revision rate of Austin-Moore hip arthroplasty (AMHA) in published literature and arthroplasty register data. A comprehensive literature analysis of clinical publications and register reports was conducted with the main endpoints revision surgery and revision rate. Sixteen relevant clinical studies have been found to significantly underestimate revision rates by a ratio of 2.15 compared to register data sets. The medium-term outcome of AMHA showed significantly worse outcomes than the use of other bipolar implants, or modular cervicocephalic prostheses and data of journal publications on revision rates deviate significantly from data of arthroplasty registers.

Interrater and intrarater reliability of the Kuntz et al new deformity classification system.

BACKGROUND Kuntz et al recently introduced a new system for classifying spinal deformities. This classification of spinal deformity was developed from age-dependent deviations from the neutral upright spinal alignment. OBJECTIVE To determine the interobserver and intraobserver reliabilities of the new Kuntz et al system for classifying scoliosis. METHODS Fifty consecutive patients were evaluated. Three observers independently assigned a major structural curve, minor structural curve, curve type, apical vertebral rotation, spinal balance, and pelvic alignment to each curve following the guidelines described by Kuntz et al. Assignment of the curves was repeated 4 weeks later, with the curves presented in a different blinded order. The Kendall W and Holsti agreement coefficients were used to determine the interobserver and intraobserver agreement. RESULTS The intraobserver value of agreement for all parameters was 0.85 (range, 0.28-1.0), and the mean Kendall W coefficient was 0.89 (range, 0.5-0.97), demonstrating perfect reliability. The interobserver agreement averaged 0.7 (range, 0.251-1.0). The mean Kendall W coefficient was 0.67 (range, 0.19-1.0), demonstrating substantial reliability. The average time for classification of 1 curve was approximately 8.4 minutes. CONCLUSION The new Kuntz et al deformity classification system is comparable to the Lenke et al system in terms of reliability. However, the Kuntz et al classification system provides no recommendations for surgical interventions. It is more complex and time-consuming and therefore may be of limited value in daily clinical practice.

Uncompromised quality of the cement mantle in Exeter femoral components implanted through a minimally-invasive direct anterior approach: A PROSPECTIVE, RANDOMISED CADAVER STUDY

A complete cement mantle is important for the longevity of a total hip replacement. In the minimally-invasive direct anterior approach used at the Innsbruck University hospital, the femoral component has to be inserted into the femoral canal by an angulated movement. In a cadaver study, the quality and the extent of the cement mantle surrounding 13 Exeter femoral components implanted straight through a standard anterolateral transgluteal approach were compared with those of 13 similar femoral components implanted in an angulated fashion through a direct anterior approach. A third-generation cementing technique was used. The inner and outer contours of the cement mantles was traced from CT scans and the thickness and cross-sectional area determined. In no case was the cement mantle incomplete. The total mean thickness of the cement mantle was 3.62 mm (95% confidence interval 3.59 to 3.65). The mean thickness in the group using the minimally-invasive approach was 0.16 mm less than that in the anterolateral group. The distribution of the thickness was similar in the two groups. The mean thickness was less on the anteromedial and anterolateral aspect than on the posterior aspect of the femur. There is no evidence that the angulated introduction of Exeter femoral components in the direct anterior approach in cadavers compromises the quality, extent or thickness of the cement mantle.