Development of a mapping function ("crosswalk") for the conversion of scores between the Oswestry Disability Index (ODI) and the Core Outcome Measures Index (COMI).

INTRODUCTION: The Oswestry Disability Index (ODI) and the Core Outcome Measures Index (COMI) are two commonly used self-rating outcome instruments in patients with lumbar spinal disorders. No formal crosswalk between them exists that would otherwise allow the scores of one to be interpreted in terms of the other. We aimed to create such a mapping function. METHODS: We performed a secondary analysis of ODI and COMI data previously collected from 3324 patients (57 ± 17y; 60.3% female) at baseline and 1y after surgical or conservative treatment. Correlations between scores and Cohen's kappa for agreement (κ) regarding achievement of the minimal clinically important change (MCIC) score on each instrument (ODI, 12.8 points; COMI, 2.2 points) were calculated, and regression models were built. The latter were tested for accuracy in an independent set of registry data from 634 patients (60 ± 15y; 56.8% female). RESULTS: All pairs of measures were significantly positively correlated (baseline, 0.73; 1y follow-up (FU), 0.84; change-scores, 0.73). MCIC for COMI was achieved in 53.9% patients and for ODI, in 52.4%, with 78% agreement on an individual basis (κ = 0.56). Standard errors for the regression slopes and intercepts were low, indicating excellent prediction at the group level, but root mean square residuals (reflecting individual error) were relatively high. ODI was predicted as COMI × 7.13-4.20 (at baseline), COMI × 6.34 + 2.67 (at FU) and COMI × 5.18 + 1.92 (for change-score); COMI was predicted as ODI × 0.075 + 3.64 (baseline), ODI × 0.113 + 0.96 (FU), and ODI × 0.102 + 1.10 (change-score). ICCs were 0.63-0.87 for derived versus actual scores. CONCLUSION: Predictions at the group level were very good and met standards justifying the pooling of data. However, we caution against using individual values for treatment decisions, e.g. attempting to monitor patients over time, first with one instrument and then with the other, due to the lower statistical precision at the individual level. The ability to convert scores via the developed mapping function should open up more centres/registries for collaboration and facilitate the combining of data in meta-analyses.

Posterior instrumentation, anterior column reconstruction with single posterior approach for treatment of pyogenic osteomyelitis of thoracic and lumbar spine.

PURPOSE: Surgical treatment of thoracolumbar osteomyelitis consists of radical debridement, reconstruction of anterior column either with or without posterior stabilization. The objective of present study is to evaluate a case series of patients with osteomyelitis of thoracic and lumbar spine treated by single, posterior approach with posterior instrumentation and anterior column reconstruction. METHODS: Seventeen patients underwent clinical and radiological evaluation pre and postoperatively with latest follow-up at 19 months (8-56 months) after surgery. Parameters assessed were site of infection, causative organism, angle of deformity, blood loss, duration of surgery, ICU stay, deformity correction, time to solid bony fusion, ambulatory status, neurologic status (ASIA impairment scale), and functional outcome (Kirkaldy-Willis criteria). RESULTS: Mean operating time was 207 min and average blood loss 1,150 ml. Patients spent 2 (1-4) days in ICU and were able to walk unaided 1.6 (1-2) days after surgery. Infection receded in all 17 patients postoperatively. Solid bony fusion occurred in 15 out of 17 patients (88 %) on average 6.3 months after surgery. Functional outcome was assessed as excellent or good in 82 % of cases. Average deformity correction was 8 (1-18) degrees, with loss of correction of 4 (0-19) degrees at final follow-up. CONCLUSIONS: Single, posterior approach addressing both columns poses safe alternative in treatment of pyogenic vertebral osteomyelitis of thoracic and lumbar spine. It proved to be less invasive resulting in faster postoperative recovery.

Adjacent vertebral fractures after percutaneous vertebral augmentation of osteoporotic vertebral compression fracture: a comparison of balloon kyphoplasty and vertebroplasty.

INTRODUCTION: It is still controversial whether adjacent level compression fractures after balloon kyphoplasty (BK) and vertebroplasty (VP) should be regarded as the consequence of stiffness achieved by augmentation with bone cement or if the adjacent level fractures are simply the result of the natural progression of osteoporosis. The purpose of this study was to evaluate the adjacent level fracture risk after BK as compared with VP and to determine the possible dominant risk factor associated with new compression fractures. MATERIALS AND METHODS: 73 consecutive patients with painful vertebral compression fractures (VCFs) were enrolled in a prospective nonrandomized study. BK was performed in 46 patients (51 vertebral bodies) and VP in 27 patients (32 vertebral bodies). The first patient's visit was before the operative procedure, when clinical and radiographical examinations were done. The follow-up visits, considered in the analysis, were on the first day and after 1 year, postoperatively. RESULTS: In 1 year, 3 out of 46 patients (6.5%) treated with BK, and 2 out of 27 patients (7.4%) treated with VP sustained adjacent level fracture. More patients with a BMD higher or equal to 3.0 experienced a new fracture than those with a BMD less than 3.0 (odds ratio = 13.00; 95% confidence interval: 1.35-124.81), and the risk for adjacent level fractures decreased significantly when the postoperative kyphotic angle was less than 9 degrees compared with that of higher or equal to 9 degrees (odds ratio = 12.00; 95% confidence interval: 1.25-114.88). CONCLUSION: Our results indicate that BK and VP are methods with a low risk of adjacent level fractures. The most important factors for new VCFs after a percutaneous augmentation procedure are the degree of osteoporosis and altered biomechanics in the treated area of the spine due to resistant kyphosis. These results suggest that the adjacent vertebrae would fracture eventually, even without the procedure. BK and VP offer a comparable rate of pain relief.

Association between sub-clinical acetabular dysplasia and a younger age at hip arthroplasty in idiopathic osteoarthritis.

This retrospective study was designed to investigate whether sub-clinical acetabular dysplasia, defined by a reduced centre-edge angle of Wiberg, was associated with a younger age at hip arthroplasty in patients with idiopathic osteoarthritis (OA). Fifty-four patients with 69 performed arthroplasties and no previous referral for hip dysplasia were selected from a list of consecutive recipients of hip endoprostheses due to idiopathic OA. The centre-edge angle was measured from standard pelvic radiographs taken a mean of 5.1 years prior to the endoprosthesis operation when there were minimal signs of hip OA. The age at which hip arthroplasty was carried out was compared between those patients with low (20 degrees - 35 degrees ) and those with high (>or= 35 degrees ) centre-edge angles. The mean age at hip arthroplasty was significantly younger in the group with centre-edge angles of 20 degrees - 35 degrees (65.6 years) compared with those with centre-edge angles >or= 35 degrees (69.2 years). These results suggest that sub-clinical acetabular dysplasia was associated with a younger age at hip arthroplasty in idiopathic OA.

The role of obesity, biomechanical constitution of the pelvis and contact joint stress in progression of hip osteoarthritis.

OBJECTIVE: The aim of our study was to explore whether earlier hip arthroplasty for idiopathic osteoarthritis (OA) might be explained by enlarged contact stress in the hip joint, and to what amount can that be attributed to obesity and biomechanical constitution of the pelvis. METHOD: Fifty subjects were selected from a list of consecutive recipients of hip endoprosthesis due to idiopathic OA; standard pelvic radiographs made years prior to surgery were the main selection criteria. For 65 hips resultant hip force and peak contact hip stress normalized to the body weight (R/Wb and p(max)/Wb) were determined from the radiographs with the HIPSTRESS method. Body weight and body mass index (BMI) were obtained with an interview. Regression analysis was used to correlate parameters of obesity (body weight, BMI), biomechanical constitution of the pelvis (R/Wb, p(max)/Wb) and mechanical loading within the hip joint (R, p(max)) with age at hip arthroplasty. RESULTS: Younger age at hip arthroplasty was associated with higher body weight (P=0.009), higher peak contact hip stress normalized to the body weight - p(max)/Wb (P=0.019), higher resultant hip force -R (P=0.027) and larger peak contact hip stress - p(max) (P<0.001), but not with BMI (P=0.121) or R/Wb (P=0.614). CONCLUSION: Our results suggest that enlarged contact stress (p(max)) plays an important role in rapid progression of hip OA with both obesity (increased body weight) and unfavorable biomechanical constitution of the pelvis (greater p(max)/Wb) contributing.

Higher peak contact hip stress predetermines the side of hip involved in idiopathic osteoarthritis.

BACKGROUND: Biomechanical parameters of the hip have been suggested to have an important influence on the development of osteoarthritis. We aimed to find out whether higher stress is generated in a hip that subsequently results in earlier hip arthroplasty compared to the contralateral hip in the same subject. METHODS: Standard anterior-posterior pelvic radiographs with no or subtle radiological signs of hip osteoarthritis, of 59 female patients, who underwent hip arthroplasty for primary osteoarthritis years later, were selected from the archives. For each subject peak contact hip stress of the hip with earlier arthroplasty and of the contralateral hip (pair of hips), was calculated from the radiographically obtained geometrical parameters with the HIPSTRESS program, which is based on a three-dimensional biomechanical model of the resultant hip force in the one-legged stance and a three-dimensional mathematical model of the contact hip stress distribution. Differences in peak contact hip stress within pairs of hips were determined for subjects with unilateral (22 pairs of hips) and bilateral disease (37 pairs of hips) by using paired-samples T-test. FINDINGS: In the population of subjects with unilateral osteoarthritis, average peak contact hip stress was significantly higher (P = 0.007) in hips with arthroplasty (2.44 kPa/N) than in contralateral hips (2.32 kPa/N). In the population of subjects with bilateral osteoarthritis, average peak contact hip stress was significantly higher (P<0.001) in hips with earlier arthroplasty (2.54 kPa/N) than in contralateral hips (2.35 kPa/N). INTERPRETATION: Results are consistent with the hypothesis that higher peak contact hip stress results in earlier hip arthroplasty due to faster development of idiopathic osteoarthritis.

Biomechanical evaluation of hip joint after Salter innominate osteotomy: a long-term follow-up study.

The biomechanical state of the hip after a Salter innominate osteotomy was investigated by using the radiographic data of 38 operated and 21 contralateral nonoperated hips from our archives. The centre-edge angle of Wiberg was determined from the radiographs taken shortly after the operation. From the radiographs of the latest follow-up (7-13 years after the operation), we also determined the peak value of contact hip joint stress normalized by the body weight, and the functional angle of the weight-bearing area. A mathematical model was used. We show that the geometrical parameters aside from the centre-edge angle may considerably influence the contact hip stress distribution. We also show that the functional angle of the weight-bearing area is a more relevant parameter than the normalized peak stress if the exact magnification of the images is not known and if there is considerable variation of the image size within the sample. The development of the centre-edge angle of the operated hips and of the contralateral hips was also studied. We found that the centre-edge angle increases on average during the follow-up time in the operated hips as well as in the contralateral nonoperated hips, but the average increase is smaller in the former. It is shown that an unfavorable stress distribution is connected to the decrease of the centre-edge angle over time. Finally, we found a weak positive correlation between the centre-edge angle shortly after the operation and the functional angle of the weight-bearing area at the of the latest follow-up.

The effect of electrostimulation and high load exercises in patients with patellofemoral joint dysfunction. A preliminary report.

Traditional conservative treatment for patellar disorders is successful in about 80 percents of cases. We introduced two new conservative treatment protocols for patellar pathology in order to further improve the success rate. The first protocol consisted of high load/low repetition quadriceps femoris training (10 patients) while the second enclosed selective electrostimulation of vastus medialis muscle (7 patients). Results were evaluated clinically and neurophysiologically. High load/low repetition training resulted in significant increase of maximal voluntary contraction of quadriceps muscle (P < 0.001). Significant gain of Activity (P = 0.017) and Kujala scores (P = 0.07) was observed in group with high load/low repetition quadriceps training compared to patients with electrostimulation. There was no significant change in neurophysiological or clinical status between the beginning and the end of treatment with electrostimulation. Our results indicate that high load/low repetition quadriceps femoris training poses an important alternative to traditional conservative treatment protocol for patellar disorders.

The assessment of contact stress in the hip joint after operative treatment for severe slipped capital femoral epiphysis.

We determined contact stress on the articular surface of the hip joint in a group of patients who underwent operative treatment for severe slipped capital femoral epiphysis. Two different procedures were considered: the modified osteotomy of Dunn-Fish and the osteotomy of Imhäuser. In order to determine the stress distribution, a three-dimensional mathematical model was used taking into account the geometrical parameters of the pelvis and hip, which were measured from standard antero-posterior radiographs. We found that the Dunn-Fish procedure produced lower peak stress than the Imhäuser procedure.

Salter osteotomy for treatment of acetabular dysplasia in developmental dysplasia of the hip in patients under 10 years.

Serial radiographs of 44 hips in 39 patients undergoing Salter innominate osteotomy for the treatment of dysplastic acetabulum owing to developmental dysplasia of the hip were reviewed. The hips were also evaluated clinically at the last follow-up examination, 7 years to 13 years postoperatively. At 7 years to 13 years postoperative, excellent or good clinical results were assessed in 43 hips (98%), and excellent or good radiographic results in 32 hips (73%). In patients with a postoperative center edge (CE) angle > 24 degrees, the CE angle remained significantly greater throughout the follow-up period compared with patients with a postoperative CE angle < or = 24 degrees. A positive correlation was found between the degree of operative CE angle correction and radiographic findings 7 years to 13 years postoperatively.

Biochemical aspects of Salter's osteotomy for treatment of acetabular dysplasia.

The center-edge (CE) angle was measured on serial antero-posterior radiographs of 44 hips treated by Salter's innominate osteotomy for developmental dysplasia of the hip. Radiographic examination according to Severin was performed and the peak hip joint pressure was calculated using geometrical parameters determined from radiographs at the most recent follow-up examination, 7 to 13 years postoperatively. At the latest follow-up assessment, there was a positive correlation between the postoperative CE angle and radiographic results. Negative correlation was found between the postoperative CE angle and peak hip joint pressure at the latest follow up. In conclusion, Salter's osteotomy performed to treat developmental dysplasia of the hip should involve radical acetabular correction resulting in maximum increase of the CE angle.

Different operative treatment of slipped capital femoral epiphysis: a comparative study of biomechanical status of the hip.

The biomechanical status of the hips subject to two different operative treatments was studied. The biomechanical status was determined by the peak stress on the weight bearing area using the 3-d mathematical model. It was found that the procedure according to Imhäuser yields considerably and statistically significantly higher peak stress than the procedure according to Dunn-Fish.

Increased muscle stiffness after anterior cruciate ligament reconstruction--memory on injury?

Residual impairment of knee function was tested in 25 patients 6 to 12 months after successful unilateral reconstruction of the anterior cruciate ligament. The control group comprised 25 healthy individuals. Jumping onto one foot from a height of 20 cm was taken as a prototype of similar everyday activities. We measured maximum flexion of the knee during the landing phase of the jump, and the degree of knee flexion at the time of maximum deceleration of the knee against gravity during jumping using the three-dimensional optical motion analysis system-ELITE. In the group of patients, measured parametres were significantly smaller on the operated side than on the unaffected side. These two measured values were significantly smaller on both legs in group of patients as compared to the values in the control group. The results of our study indicate that functional disturbance persisted for 6 to 12 months after anterior cruciate reconstruction. This may be due to the changed muscle activation pattern of the knee causing increased stiffness of knee muscles. It seems that re-programming of the central nervous system occurred in order to protect the injured lower extremities from another injury.