Dynamic stabilization of the lumbar spine.

This study analyzed the outcome of patients treated with total disk replacement and posterior dynamic stabilization. For pathologies of different origin, dynamic stabilization of the lumbar spine is a novel alternative to fusion surgery. Although a physiological reconstruction of the sagittal profile was not always achieved, improvement was seen in all subscales of the clinical outcome measures in both treatment groups. Posterior dynamic stabilization and total disk replacement are promising alternatives to fusion with acceptable morbidity for strictly defined indications.

Evaluation of lumbar spine motion with dynamic X-ray--a reliability analysis.

STUDY DESIGN: Radiologic evaluation of lumbar range of motion (ROM) with dynamic radiograph. OBJECTIVES: To calculate 95% confidence intervals (CIs) for the measurement error accompanying different methods, different observers, and different levels of training when measuring sagittal plane segmental ROM in lumbar spine. In addition, to compare the 95% CI with frequently common statistical methods of reliability analysis. SUMMARY OF BACKGROUND DATA: Dynamic radiographs are commonly used for ROM calculation of the lumbar spine. Yet, the reliability of different measurement methods still remains unclear. METHODS: In 24 patients, levels L4-L5 and L5-S1 were measured with the Cobb and superimposition methods on flexion-extension radiographs. There were 2 experienced and 1 inexperienced observer that performed the measurements. The 95% CIs were compared with the corresponding Pearson correlation coefficient and P value (t test). RESULTS: The 95% CI of the superimposition method was +/-4.0 degrees for the experienced and +/-4.7 degrees for the inexperienced observer. The corresponding values for the Cobb method was +/-4.2 degrees for the experienced and +/-6.8 degrees for the inexperienced observer. The 95% CI for the measurement error became even worse when different methods or observers were compared, whereas a method constancy revealed superior reliability than observer constancy in experienced observers. CONCLUSIONS: For lumbar ROM measurement with dynamic radiograph, the superimposition method seems to be more reliable than the Cobb method. Study protocols dealing with ROM measurement have to calculate the 95% CI of the measurement method used because clinically valid conclusions can only be drawn with respect to these intervals.

Reliability of the Crowe und Hartofilakidis classifications used in the assessment of the adult dysplastic hip.

OBJECTIVE: To assess the inter-observer and intra-observer reliability of two commonly used radiographic classification systems in the evaluation of hip dysplasia in skeletally mature adults. DESIGN: Three observers with different levels of training independently classified 62 dysplastic hips on 51 standard anteriorposterior pelvis radiographs according to the criteria defined by Crowe and by Hartofilakidis. To assess intra-observer reliability, the same radiographs were reviewed 3 months later by the same observers. PATIENTS: At the time of the radiographic examination, the mean age of the 51 patients had been 54 years (range 18-82 years). RESULTS: A high correlation concerning the inter- and intra-observer reliability of both systems was demonstrated. Inter-observer reliability displayed a weighted kappa coefficient of 0.82 for the Crowe and 0.75 for the Hartofilakidis classification. Intra-observer reliability showed a kappa coefficient of 0.86 and 0.79, respectively. CONCLUSIONS: Both classification systems can be recommended to compare collectives of adult patients with congenital dysplasia of the hip. However, for future clinical practice, it would be advisable to agree on one universally accepted system as a standard in the literature.

Changes in strain distribution of loaded proximal femora caused by different types of cementless femoral stems.

BACKGROUND: A number of clinically used total hip femoral implants are claiming a more or less physiologic load transfer, mostly without providing experimental data. To compare three clinically cementless total hip stems of fundamentally different design, the strain distribution before and after insertion in human cadaver femora was measured in vitro. METHODS: A conventional straight stem based on a distal anchorage concept, a so-called "anatomic" stem designed to have a proximal force transmission and a "stemless" femoral neck prosthesis were evaluated under similar loading conditions. Strain distribution was measured with tri-axial strain-gauge rosettes before and after implantation of the stems. The same bending moment was used in all femora tested to compare magnitude and direction of the resulting strains. FINDINGS: The straight and the "anatomic" stem both led to a decrease of the longitudinal strains in the proximal femur, while the femoral neck implant mainly led to an increase of measured strains on the lateral side of the greater trochanter. The observed medial strains were closer to physiological values in the "stemless" prosthesis than those of the two full-stem prosthesis. INTERPRETATION: The decrease in strains seen in the proximal region of the femora with implanted conventional hip prosthesis corresponds well to the decrease of bone density in this region noted in clinical follow-up studies. The more physiological strain at the inferior base of the neck seen in "stemless implant" may induce a remodelling process that better retains bone stock in that area. However, the increase of strains noted after implantation of this prosthesis require further investigation to assess the risk they may pose to bone failure.

Posterior atlantoaxial three-point fixation: comparison of intraoperative performance between open and percutaneous techniques.

INTRODUCTION: Atlantoaxial instabilities, which require surgical fixation follow a variety of clinical disorders. Different surgical procedures are used for stabilization of the atlantoaxial complex, mainly posterior wiring techniques and transarticular screw fixation. Nowadays, often a combination of transarticular screws and a posterior one-point fixation is used to achieve a three-point fixation, with superior biomechanical stability and good clinical results. Different modifications were developed to improve this technique. In 1995, a percutaneous approach for atlantoaxial stabilization was introduced. In clinical studies, the technique showed a tendency towards better outcome. Beside the outcome, the intraoperative performance is of special interest for minimal invasive approaches. We therefore compared the operation time, screw angulation and blood loss, between the open and percutaneous posterior atlantoaxial techniques. MATERIALS AND METHODS: Two groups, each consisting of 17 patients, with either open (group 1) or percutaneous (group 2) atlantoxial stabilization, were compared. The operation time was retrospectively acquired from the patient's charts. The data for blood loss was provided by our anaesthesiological department, separated for intraoperative, postoperative and total blood loss. Screw angulation was measured on the postoperative x-ray by an orthopaedic surgeon. RESULTS: The percutaneous group showed an average intraoperative blood loss of 239.7 ml, compared to 929.4 ml for the open group (p< or =0.001). The analogue values for the postoperative blood loss were 142.9 ml and 379.4 ml for group 2 and group 1, respectively (p=0.008). Consecutively, the total blood loss showed also a statistically significant difference (p< or =0.001). The operation time was significantly different (p< or =0.001), with average values of 175.3 min (group 1) and 110.6 min (group 2). Screw angulation showed a trend towards a steeper angulation in the percutaneous group with an average angle of 56.8 degrees , compared to 53.9 degrees (group 1), although this was not statistically significant (p=0.053). CONCLUSION: The percutaneous technique for atlantoaxial stabilization with a three-point fixation has clear intraoperative benefits, with shorter operation time and reduced blood loss. A trend towards steeper screw angulation was found and shows at least equal feasibility for transarticular screw placement with the percutaneous technique, compared to the standard open approach.

Reliability of motion measurements after total disc replacement: the spike and the fin method.

As motion preservation is one of the main postulated advantages after total disc replacement (TDR) of the lumbar spine, the quantification of the mobility after TDR seems of special clinical interest. Yet, the best method to assess range of motion (ROM) after TDR remains unclear. The aim of the study was the calculation of 95%-confidence intervals (95%-C.I.) for the measurement error accompanying: (1) different methods (2) different observers and (3) different levels of training for radiographic motion analysis after TDR. In 12 patients the level L4-L5 and in another 12 patients level L5-S1 were measured with the Cobb and the superimposition method on flexion-extension X-rays after monosegmental TDR. Both methods were adopted as the landmarks used the spikes of the prosthesis instead the endplates (spike method) and the fin of the prosthesis instead the whole vertebral body (fin method). Measurements were performed by two experienced (O-I and O-III) and one inexperienced observer (O-II). The adopted spike and fin method showed a better reliability compared to the reported results of the original Cobb and superimposition method. The method used was not clinically relevant for the intraobserver reliability in the experienced observer (95%-C.I.: +/-2.0 degrees for the fin and +/-2.1 for the spike method) and for the interobserver reliability for two experienced observers (95%-C.I.: -2.8 degrees /+2.8 degrees for the fin and -2.9 degrees /+3.1 degrees for the spike method). The intraobserver reliability for the inexperienced observer was inferior for both methods compared to the experienced observer but no clinically relevant differences could be observed in interobserver reliability measures. The spike and fin method are reliable methods for study protocols dealing with angular motion after TDR as clinically valid conclusions can be drawn with an accuracy of about +/-2 degrees for the same observer and with an accuracy of about +/-3 degrees for a different observer.

Efficacy and cost effectiveness of harmonic scalpel compared with electrocautery in posterior instrumentation of the spine.

Different methods to reduce blood loss during spinal surgery have been described already. Although the use of the harmonic scalpel (HS), an ultrasonically activated coagulator, has been described in endoscopic spinal surgery, its efficacy in posterior instrumentation of the spine remains unclear. The aim of this study was to determine if blood loss was lower using the HS than electrocauterization (EC) and to evaluate the cost effectiveness of the HS in reducing the need for transfusion in patients undergoing posterior instrumentation of the spine. The two groups were matched in a blinded manner, without knowledge of blood loss and were similar with respect to mean age, diagnosis and operation data. All instrumentations were done by the same surgeon. After matching was completed (HS group n = 50, EC group n = 50) blood loss and overall costs for blood products were analyzed by independent observers. The following were significantly lower with the HS than with EC: (1) blood loss (1106+/-985 ml vs 2176+/-1764 ml, P < 0.001), (2) frequency of cell saver use (13 vs 28 patients, P = 0.001), (3) average cost of blood products (Euro 72 vs Euro 219, P < 0.001), (4) predonation of autologous fresh frozen plasma (2.58+/-2.78 vs 4.5+/-2.2 U, P = 0.002) and red blood cells (0.38+/-0.75 vs 0.88+/-1.1 U, P = 0.009). The overall costs, including the costs for the HS, remained neutral. The use of the HS in posterior spinal surgery leads to significantly lower blood loss, and less need for and cost of blood products, compared to EC in cases with major anticipated blood loss.

The Tokuhashi score: significant predictive value for the life expectancy of patients with breast cancer with spinal metastases.

STUDY DESIGN: Retrospective study of 55 consecutive patients with spinal metastases secondary to breast cancer who underwent surgery. OBJECTIVE: To evaluate the predictive value of the Tokuhashi score for life expectancy in patients with breast cancer with spinal metastases. SUMMARY OF BACKGROUND DATA: The score, composed of 6 parameters each rated from 0 to 2, has been proposed by Tokuhashi and colleagues for the prognostic assessment of patients with spinal metastases. METHODS: A total of 55 patients surgically treated for vertebral metastases secondary to breast cancer were studied. The score was calculated for each patient and, according to Tokuhashi, the patients were divided into 3 groups with different life expectancy according to their total number of scoring points. In a second step, the grouping for prognosis was modified to get a better correlation of the predicted and definitive survival. RESULTS: Applying the Tokuhashi score for the estimation of life expectancy of patients with breast cancer with vertebral metastases provided very reliable results. However, the original analysis by Tokuhashi showed a limited correlation between predicted and real survival for each prognostic group. Therefore, our patients were divided into modified prognostic groups regarding their total number of scoring points, leading to a higher significance of the predicted prognosis in each group (P < 0.0001), and a better correlation of the predicted and real survival. CONCLUSION: The modified Tokuhashi score assists in decision making based on reliable estimators of life expectancy in patients with spinal metastases secondary to breast cancer.

Distractible vertebral body replacement for the thoracic and lumbar spine.

We retrospectively evaluated the results after corporectomy and vertebral body replacement in 40 patients with thoracic or lumbar spine collapse due to tumour osteolysis, unstable fractures, spondylodiscitis and Paget's disease. They underwent posterior transpedicular instrumentation followed 7 to 21 days later by vertebral body replacement with a distractible device, the "Obelisc" cage, filled up with autogenous/allogeneic bone graft. The mean residual kyphosis after surgery was only 13.8 degrees. After a mean follow-up period of 16.3 months, there was a mean loss of correction of 1.1 degrees. Perioperative complications occurred in 25 patients (62.5%); one died of septic shock, and the others were treated conservatively. Postoperatively, neurological improvement was noted in 8 patients. Using this in situ distractible vertebral body replacement system to achieve intraoperative stabilisation, neurological improvement and minimal postoperative displacement were achieved with an acceptable perioperative risk.

Posterior stabilisation of a malignant cervico-thoracic vertebral bone defect.

Oesophageal cancer is frequently complicated by malignant fistulae. Necrosis of the tumour following radiotherapy or chemotherapy may lead to the development of fistulae between the oesophagus and adjacent tissues and organs. We report the expansion of an extra-luminal oesophageal cancer after resection, invading the cervico-thoracic spine, fortunately without neurological deficit, and leading to instability and formation of a malignant fistula linking the tracheo-bronchial tree to the subarachnoidal space. To prevent imminent paraplegia and to alleviate severe pain, we rigidly stabilised the spine at the cervico-thoracic junction using an angle-stable system through a single posterior approach. Further postoperative follow-up revealed no signs of neurological deterioration. Cervico-thoracic stability was preserved until the patient died nearly five months postoperatively. This case shows that posterior stabilisation and decompression may be a palliative option for patients with imminent paraplegia and severe pain due to advanced tumour infiltration of the cervico-thoracic spine.

Limitations of the cervical porcine spine in evaluating spinal implants in comparison with human cervical spinal segments: a biomechanical in vitro comparison of porcine and human cervical spine specimens with different instrumentation techniques.

STUDY DESIGN: Porcine and human cervical spine specimens were in vitro biomechanically compared with different instrumentation techniques. OBJECTIVES: To evaluate whether subaxial porcine cervical spines are a valid model for implant testing in a single level corpectomy. SUMMARY OF BACKGROUND DATA: Biomechanical in vitro tests are widely used for implant tests, mainly with human spine specimens. The availability of human cadavers is limited and the properties of the specimen regarding age, bone mineral density, and grade of degenerative changes is inhomogeneous. METHODS: Six porcine and six human cervical specimens were loaded nondestructively with pure moments: 1) in an intact state; 2) after a corpectomy of C5 and substitution by a cage with integrated force sensor; 3) after additional instrumentation with a posterior screw and rod system with: a) lateral mass and b) pedicle screws; 4) after instrumentation with an anterior plate; and 5) with a circumferential instrumentation. The unconstrained motion and the axial loads occurring in the corpectomy gap were measured, as well as the bone mineral density of the specimen before testing. RESULTS: The range of motion in the intact state, as well as for the different instrumentations, was comparable for flexion-extension. In lateral bending and axial rotation, marked differences in the intact state as well as for pedicle screw instrumentations occurred. CONCLUSIONS: The subaxial porcine cervical spine is a potential model in flexion-extension because of its biomechanical similarity. For lateral bending and axial rotation, the marked differences severly restrict the comparability.

Leg axis after computer-navigated total knee arthroplasty: a prospective randomized trial comparing computer-navigated and manual implantation.

To compare the alignment after computer-navigated total knee arthroplasty, 52 patients were randomly allocated to 2 groups. Twenty-seven patients received a total knee arthroplasty with the aid of a kinematic computer-navigation system, and 25 patients received a total knee arthroplasty with the conventional method. Both groups were well balanced concerning demographic data and preoperative scores. At 3-month follow-up, the mechanical alignment of the leg reached the desired straight axis in more cases with the computer-navigated implantation. This difference was statistically significant. The femoral and tibial mechanical anteroposterior axis and the femoral and tibial sagittal tilt (slope) measured on sagittal x-rays were not significantly improved in this patient group.

Assessment of femoral component migration in total hip arthroplasty: digital measurements compared to RSA.

The aim of this study was to determine the accuracy of the software system "Düsseldorf Migration Analysis - Femoral Component Analysis" (DMA-FCA) in measuring stem migration in total hip arthroplasty (THA) on digitised anteroposterior radiographs of the pelvis. Bony and implant landmarks on two consecutive radiographs were used for measurements of subsidence and varus-valgus tilt. The accuracy of the method was determined by reference to radiostereometric measurements (RSA). Using specific comparability limits, comparability analysis of radiographs with respect to femoral positioning is possible with DMA. DMA-FCA and RSA measurements were performed after cementless THR in a population of 60 patients aged 38 to 69 years. With a Cronbach's alpha-index of 0.89 and 0.99 for subsidence and 0.90 and 0.98 for classic varus-valgus-tilt, the intraobserver and interobserver reliability for the DMA-FCA-method was calculated as good. Using RSA as reference method, the accuracy of DMA-FCA was calculated to be 2.51 mm for subsidence and 2.49 degrees for varus-valgus-tilt (95% confidence interval). Without comparison to RSA, DMA measured 1.94 mm for subsidence and 2.35 degrees for varus-valgus-tilt. Based on a comparison with RSA, our results show lower accuracy for DMA-FCA than for EBRA-FCA, but DMA-FCA is easier to use in everyday clinical practice. It is hoped that the use of digital measuring methods such as DMA will become standard for long-term observation and will be integrated into clinical routine in the context of quality assurance of THR.

The impact of total lumbar disc replacement on segmental and total lumbar lordosis.

BACKGROUND: One of the goals of total lumbar disc replacement is restoration of the physiological sagittal alignment. There is little evidence if this goal is reached in vivo and further affects the clinical outcome. METHODS: In 29 patients segmental lordosis and total lumbar lordosis were measured on X-rays pre- and postoperatively. The functional outcome was evaluated prospectively with the Visuell Analogue Scale, Oswestry Low Back Pain Disability Questionnaire and Short Form 36 Health Survey Questionnaire. FINDINGS: Total disc replacement increased segmental lordosis significantly while total lumbar lordosis remained unchanged. Preoperative segmental/total lumbar lordosis was physiological in 52%/91% of the patients. Postoperatively these values changed to 72% for segmental- and 94% for total lumbar lordosis. No difference could be observed in clinical outcome measures in patients with physiological and unphysiological segmental lordosis. INTERPRETATION: Monosegmental total disc replacement increases the segmental lordosis in most of the cases while preserving the total lumbar lordosis which produces a decrease of lordotic angle in the adjacent segment(s). Although short term clinical results are not affected, the segmental lordosis increase and adjacent segment(s) alteration may influence long term outcome.

Effect of constrained posterior screw and rod systems for primary stability: biomechanical in vitro comparison of various instrumentations in a single-level corpectomy model.

Cervical corpectomy is a frequently used technique for a wide variety of spinal disorders. The most commonly used approach is anterior, either with or without plating. The results for single-level corpectomy are better than in multilevel procedures. Nevertheless, hardware- or graft-related complications are observed. In the past, constrained implant systems were developed and showed encouraging stability, especially for posterior screw and rod systems in the lumbar spine. In the cervical spine, few reports about the primary stability of constrained systems exist. Therefore, in the present study we evaluated the primary stability of posterior screw and rod systems, constrained and non-constrained, in comparison with anterior plating and circumferential instrumentations in a non-destructive set-up, by loading six human cadaver cervical spines with pure moments in a spine tester. Range of motion and neutral zone were measured for lateral bending, flexion/extension and axial rotation. The testing sequence consisted of: (1) stable testing; (2) testing after destabilization and cage insertion; (3a) additional non-constrained screw and rod system with lateral mass screws, (3b) with pedicle screws instead of lateral mass screws; (4a) constrained screw and rod system with lateral mass screws, (4b) with pedicle screws instead of lateral mass screws; (5) 360 degrees set-up; (6) anterior plate. The stability of the anterior plate was comparable to that of the non-constrained system, except for lateral bending. The primary stability of the non-constrained system could be enhanced by the use of pedicle screws, in contrast to the constrained system, for which a higher primary stability was still found in axial rotation and flexion/extension. For the constrained system, the achievable higher stability could obviate the need to use pedicle screws in low instabilities. Another benefit could be fewer hardware-related complications, higher fusion rate, larger range of instabilities to be treated by one implant system, less restrictive postoperative treatment and possibly better clinical outcome. From a biomechanical standpoint, in regard to primary stability the constrained systems, therefore, seem to be beneficial. Whether this leads to differences in clinical outcome has to be evaluated in clinical trials.

Minimally invasive intervention for acute bleeding from a pseudoaneurysm after revision hip arthroplasty.

After multiple revisions of her right hip arthroplasty, an 83-year-old woman developed deep infection with a chronic draining sinus. In August 2002 severe acute bleeding occurred through this fistula. Angiography revealed a pseudoaneurysm of the right external iliac artery. Because of the multiple pathologies affecting this ASA grade IV patient, conventional surgical treatment was considered to be contra-indicated, and a stent was placed percutaneously under fluoroscopic control to seal the vascular laceration. No haematoma and no further bleeding was observed on the control CT-scan or at angiography. However the patient died with terminal renal failure forty days later. The case reported shows a rare complication of total hip arthroplasty. The method used in this case to seal the leakage, using a covered stent, is uncommon but effective in cases where conventional surgery is contra-indicated.

Influence of operation duration on perioperative morbidity in revision total hip arthroplasty.

This retrospective study investigated the impact of patient and procedure-related parameters on the complication rate following revision total hip arthroplasty. Complications included vessel and nerve damage, periprosthetic femoral fracture, wound infection, wound bleeding, prosthesis dislocations, thromboembolism, cardiac and pulmonary complications, and death. The influence of operation duration, gender, revision status, ASA classification, and type of fixation of the primary implant on the perioperative morbidity was investigated in a sample of 60 revision procedures (cemented stems, cemented or cementless cups). Odds ratio [OR] and 95% confidence interval [CI] were estimated with multiple regression models. Perioperative morbidity was significantly correlated to operation duration (OR = 1.03; CI: 1.00-1.05), but not to age (OR = 1.01; CI: 0.93-1.09), gender (OR = 2.66; CI: 0.50-14.05), revision status (OR = 2.34; CI: 0.54-10.05), ASA classification (OR = 1.24; CI: 0.30-5.18), or type of fixation of the primary implant (OR = 2.49; CI: 0.47-13.17) Duration of the revision operation appeared as a predictive parameter for perioperative morbidity in revision total hip arthroplasty in our study group.

Pedicle screws enhance primary stability in multilevel cervical corpectomies: biomechanical in vitro comparison of different implants including constrained and nonconstrained posterior instumentations.

STUDY DESIGN: 6 human cervical spines were tested in vitro in a biomechanical nondestructive set-up to compare different anterior, posterior and combined instrumentations after a corpectomy C4-C6. OBJECTIVES: To evaluate the primary three-dimensional stability of the different instrumentations. SUMMARY OF BACKGROUND DATA: The clinical results after stabilization of multilevel corpectomies are often disappointing. Higher biomechanical stability could enhance the rate of successful outcomes. The best instrumentation for these high-grade instabilities has yet to be found. METHODS: Six human cervical specimens were loaded nondestructively with pure moments and unconstrained motion at C3/7 was measured. The six specimens were instrumented with each of the following fixation techniques: 1. Cage 2. Nonconstrained posterior screw and rod system with lateral mass (NC-LM) 3. and pedicle screws (NC-P) 4. Constrained posterior screw and rod system with lateral mass (C-LM) and 5. pedicle screws (C-P) 6. Circumferential (C-P and anterior plate) 7. Anterior plate (OAP). RESULTS: For flexion/extension and axial rotation the circumferential instrumentation showed lowest ROM values, followed by C-P. The use of pedicle screws showed only a lower ROM when using the constrained system. No difference was found between the two screw types in the nonconstrained system. The anterior plating had the lowest stabilizing effect of all instrumentations, except for the cage alone. CONCLUSIONS: Usage of pedicle screws enhances primary stability only when using an constrained screw and rod system. In axial rotation the nonconstrained system showed no distinct difference compared to the intact state, independent of the screw type.

PTHrP, PTHr, and FGFR3 are involved in the process of endochondral ossification in human osteophytes.

To elucidate the process of endochondral ossification in human osteophytes we have studied the expression of parathyroid hormone-related protein (PTHrP), its receptor (PTHr), and fibroblast growth factor receptor 3 (FGFR3). Osteophytes from patients undergoing total knee replacement ( n=13), and fetal growth plate cartilages ( n=4) were processed for safranin O staining and immunohistochemistry. Chondrocytes and their matrix were preferentially stained for PTHrP in the middle and deep zones of the osteophytes examined. Ossified areas did not show a positive staining. In fetal joints the cartilaginous surface and the perichondrium as well as the osteoblasts in the trabecular bone were positive. PTHr was expressed at large in chondrocytes and osteoblasts of all osteophytes and fetal joints. Cells of the perichondrium were also positive. The FGFR3 antibody stained only single chondrocytes in some osteophytes, and groups of cells in others. In fetal samples, chondrocytes of the proliferating and the hypertrophic zone showed staining for FGFR3. This is the first report on the expression of PTHrP, PTHr, and FGFR3 in human osteophytes. As in fetal joints these mediators might regulate proliferation and differentiation of chondrocytes playing an important role in osteo(chondro)phyte growth.