Bone tunnel placement influences shear stresses at the coracoid process after coracoclavicular ligament reconstruction: a finite element study and radiological analysis.

INTRODUCTION: Coracoid fractures after arthroscopic treatment of acromioclavicular (AC) joint separations lead to poor clinical outcomes. In this study, different configurations of bone tunnels in the lateral clavicle and coracoid were examined concerning the amount of stress induced in the coracoid. METHODS: An authentic 3D finite element model of an ac joint was established. Three 2.4 mm bone tunnels were inserted in the lateral clavicle, which were situated above, medially and laterally of the coracoid. Then, two 2.4 mm bone tunnels were inserted in the latter, each simulating a proximal and a distal suture button position. Von Mises stress analyses were performed to evaluate the amount of stress caused in the coracoid process by the different configurations. Then, a clinical series of radiographs was examined, the placement of the clavicle drill hole was analyzed and the number of dangerous configurations was recorded. RESULTS: The safest configuration was a proximal tunnel in the coracoid combined with a lateral bone tunnel in the clavicle, leading to an oblique traction at the coracoid. A distal bone tunnel in the coracoid and perpendicular traction as well as a proximal tunnel in the coracoid with medial traction caused the highest stresses. Anatomical placement of the clavicle drill hole does lead to configurations with smaller stresses. CONCLUSION: The bone tunnel placement with the smallest amount of shear stresses was found when the traction of the suture button was directed slightly lateral, towards the AC joint. Anatomical placement of the clavicle drill hole alone was not sufficient in preventing dangerous configurations. LEVEL OF EVIDENCE: Controlled laboratory study.

A biomechanical comparison of steel screws versus PLLA and magnesium screws for the Latarjet procedure.

INTRODUCTION: The fixation of the coracoid process onto the glenoid is an important step of the Latarjet procedure, and implant-associated complications are a relevant and severe problem. This study compares the fixation strength and failure mode of two biodegradable materials with stainless-steel screws. METHODS: 24 Fresh-frozen cadaveric scapulae were divided into three groups of equal size and received a coracoid transfer. Cadavers were matched according to their bone mineral density (BMD). In group 1, small-fragment screws made of stainless steel were used. In the second group, magnesium screws were used, and in the third group, screws consisted of polylactic acid (PLLA). A continuously increasing sinusoidal cyclic compression force was applied until failure occurred, which was defined as graft displacement relative to its initial position of more than 5 mm. RESULTS: At 5-mm displacement, the axial force values showed a mean of 374 ± 92 N (range 219-479 N) in group 1 (steel). The force values in group 2 (magnesium) had a mean of 299 ± 57 N (range 190-357 N). In group 3 (PLLA), failure occurred at 231 ± 83 N (range 109-355 N). The difference between group 1 (steel) and group 2 (magnesium) was not statistically significant (P = 0.212), while the difference between group 1 (steel) and group 3 (PLLA) was significant (P = 0.005). CONCLUSION: Stainless-Steel screws showed the highest stability. However, all three screw types showed axial force values of more than 200 N. Stainless steel screws and PLLA screws showed screw cut-out as the most common failure mode, while magnesium screws showed screw breakage in the majority of cases. EVIDENCE: Controlled laboratory study.

[Pedicle screw augmentation from a biomechanical perspective]. / Pedikelschraubenaugmentation aus biomechanischer Sicht.

Severe osteoporosis is a serious problem in the instrumentation during spine surgery. Besides kyphosis, adjacent vertebral fractures and of course pedicle screw loosening and implant pullout are frequent challenges in instrumentation of the osteoporotic spine. In addition to screw diameter and length, bone mineral density has the most important impact on the stability of a pedicle screw. In cases of severe osteoporosis cement augmentation increases the stability of a pedicle screw. Pullout force can be increased with augmentation by 96-278%. Nowadays, there are two different procedures for augmentation: cement augmentation of the vertebra before inserting the screw into the soft, fresh cement or augmentation via a perforated screw that has already been inserted.The main problem in augmentation techniques are cement leakages. In both techniques leakages may occur. The problem of leakages seems to be less severe in the augmentation technique via the perforated screw, because cement application can be stopped immediately if the onset of leakage is noticed. Even surgical revision of cement augmented screws is not a major clinical problem based on recent biomechanical studies. The revision screw can be chosen 1 mm thicker and can be cement augmented again without technical problems.

[Posterior operative correction of idiopathic scoliosis. Value of pedicle screws versus hooks]. / Dorsale operative Korrektur der idiopathischen Skoliose. Stellenwert von Pedikelschrauben vs. Haken.

Posterior correction and fusion of scoliosis with multisegmental instrumentation systems was developed by Cotrel-Dubousset in the 1980s. Initially correction and instrumentation was performed using hooks only. Later pedicle screws were implemented first for the lumbar and then for the thoracic spine. Nowadays instrumentation based on pedicle screws only is well established for posterior scoliosis surgery. Biomechanical studies demonstrated higher pull-out forces for pedicle than for hook constructs.In clinical studies several authors reported better Cobb angle correction of the primary and the secondary curves and less loss of correction in pedicle screw versus hook instrumentations. Furthermore, pedicle screw instrumentation allows fewer segments to be fused, especially caudally, and thus saving mobile segments. In most of these publications there were no differences in operation time, blood loss and complication rates. In summary, there is better curve correction without an increased risk using multisegmental pedicle screw instrumentation in modern posterior scoliosis surgery.

[Value of adjuvant physiotherapy in postoperative pain management]. / Stellenwert der physikalischen Therapie und Physiotherapie in der postoperativen Schmerztherapie.

In times of limited financial and human resources the application of adjuvant physiotherapy postoperatively in orthopaedic patients requires reevaluation. In the early postoperative course physiotherapy improves the patients' mobility. However, it is not able to reduce the need for pain medication. It is intended to minimize complications and to mobilize and motivate the patients early. In contrast, massages are of minor importance in the immediate postoperative course and are applied only in a few selected cases. Cryotherapy plays a major role especially after shoulder and knee surgery. On the other hand, transcutaneous electrical nerve stimulation (TENS) and acupuncture are applied only in selected patients after orthopaedic surgery, e.g., after limb amputation.

Increased risk of myeloid leukaemia in patients with ankylosing spondylitis following treatment with radium-224.

OBJECTIVE: To investigate long-term health effects in AS patients treated with (224)Ra. METHODS: A prospective epidemiological study has been carried out on 1471 AS patients treated with repeated intravenous injections of (224)Ra between 1948 and 1975. These patients have been followed together with a control group of 1324 AS patients not treated with radioactive drugs and/or X-rays. Numbers of malignancies expected in a normal population were computed from German and Danish cancer registry data. RESULTS: After a mean follow-up time of 26 yrs in the exposed group or 25 yrs in the control group, causes of death have been ascertained for 1006 exposed patients and 1072 controls. In particular, 19 cases of leukaemia were observed in the exposure group (vs 6.8 cases expected, P < 0.001) compared to 12 cases of leukaemia in the control group (vs 7.5 cases expected). Further subclassification of the leukaemia cases demonstrated a high increase of myeloid leukaemia in the exposure group (11 cases observed vs 2.9 cases expected, P < 0.001), especially a high excess of acute myeloid leukaemias (7 cases observed vs 1.8 cases expected, P = 0.003), whereas in the controls the observed cases are within the expected range (4 myeloid leukaemias vs 3.1 cases expected). CONCLUSIONS: The enhanced leukaemia incidence in the exposed group is in line with results from experiments in mice injected with varying amounts of the bone-seeking alpha-emitter (224)Ra. In these studies, in animals exposed to lower doses of (224)Ra, i.e. at doses lower than those found to induce osteosarcomas, an increased risk of leukaemia was observed.

Injection therapy of lumbar facet syndrome: a prospective study.

BACKGROUND: Chronic low back pain remains a major health problem. Facet joint injection therapy is an easy to perform therapeutic option. However, few prospective studies use a standardized protocol to investigate injection therapy. The aim of our study was to evaluate quantity and duration of clinical improvement after this protocol, and to identify the best time for additional repetitive injection therapy. MATERIALS AND METHODS: Thirty-nine patients (21 men, 18 women; mean age 55.2 years [range, 29-87 years]) with lumbar facet syndrome were treated with injection using a standardized protocol (prednisolone acetate, lidocaine 1%, phenol 5%) under fluoroscopic control. Follow-up was based on a specially designed questionnaire. Analysis included MacNab criteria, visual analogue scale, and pain disability index. RESULTS: Reduction of pain was found up to 6 months after treatment. The outcome was assessed excellent or good by 62% (24 patients) of the patients after 1 month, by 41% (16 patients) after 3 months, and by 36% (14 patients) after 6 months. There was no influence of age, body mass index, or previous lumbar spinal surgery on improvement after treatment. There were no severe side effects. Short-lasting self limiting mild side effects were found in 26% (increased back pain, numbness, heartburn, headache, allergy). CONCLUSION: Facet joint injection therapy using a standardized protocol is safe, effective, and easy to perform. The clinical effect is limited, and we recommend repetitive injection according to this protocol after 3 months.

[Lumbar spinal stenosis]. / Lumbale Spinalkanalstenose.

Lumbal spinal stenosis is gaining more and more clinical relevance because of changing population structure and increasing demand on lifequality in the elderly. Current treatment recommendations are based on clinical experience, expert opinions and single studies rather than on proven evidence. The radiologic degree of stenosis does not correlate with the patients' clinical situation. It is not the main factor indicating surgery but rather the typical history and spinal claudication. Symptomatic patients with light to moderate complaints should undergo multimodal conservative treatment. Epidural injections, delordosating physiotherapy and medication are useful. In patients with severe symptomatic stenosis surgery is indicated after a conservative treatment of 3 months. Relevant pareses or a cauda equina syndrome are absolute indications for surgery. The general aim is to decompress sufficiently while maintaining or restoring segmental stability. A laminectomy is not necessarily required. In patients with accompanying degenerative Meyerding grade I-II spondylolisthesis or instability in functional radiographs, fusion or dynamic stabilisation are recommended in addition to decompression, depending on the patient's age and activity level.

Transient tetraplegia and vegetative dysfunction depending on cervical positioning caused by a cervical spinal chordoma.

A 39-year-old man with acquired torticollis suffering from cervicobrachialgia and neurological deficits is presented. Due to a change in head position a transient reproducible tetraplegia and severe vegetative dysfunctions were caused. The origin of this uncommon serious combination of symptoms and signs was a chordoma of the upper cervical spine. After surgical decompression the patient was free of neurological deficit and pain. Review of the literature did not reveal any similar case.

Acute compartment syndrome following intramedullary pulse lavage and débridement for osteomyelitis of the tibia.

The implantation of gentamicin loaded polymethylmethacrylate (PMMA) beats and other local antibiotic carriers is a common practice in the treatment of chronic osteomyelitis as is the use of local jet lavage débridement. This article presents the case of a patient with chronic osteomyelitis of the tibia, who had no complication after débridement, intramedullary reaming and pulse lavage without tourniquet but sustained a compartment syndrome 2 weeks later during a second procedure in which an intraoperative tourniquet and pulse lavage were combined.

[Lumbar disc arthroplasty. Established technique or experimental procedure?]. / Lumbale Bandscheibenprothesen. Etablierte Technik oder experimentelles Vorgehen?

Lumbar interbody fusion used to be the most common surgical treatment for painful lumbar disc degeneration. With the technical development of total disc prostheses, replacement of the degenerated disc by a motion preserving implant has become a widely discussed alternative. The advantages of such replacement appear to include the prevention of adjacent segment disease as well as less perioperative morbidity. Three types of total disc prostheses are currently in common use. Although numerous studies have been made, a review of the literature reveals only two multicenter randomized studies comparing the outcome of disc prostheses with a control group of fusion patients. After 2 years, the available results show similar improvement after both types of surgery without significant differences. However, there is a trend towards faster recovery and improvement in disc arthroplasty patients. The long-term results of current and future randomized studies, including studies comparing results after disc arthroplasty, with results of standardized conservative therapies will determine the fate of lumbar disc prostheses.

Comparison of metric analysis of spinal structures, exemplarily of the ligamentum flavum, obtained with CT and MRI.

PURPOSE: Comparison of metric analysis of spinal structures, exemplarily of the ligamentum flavum, obtained with computed tomography (CT) (soft tissue window and bone window) and magnetic resonance imaging (MRI) (T1 and T2 weighted images). MATERIAL AND METHODS: Forty-six lumbar ligamenta flava of 46 patients (25 women and 21 men) were examined at a Somatom Plus 4 (Siemens, Erlangen, FRG) and at a 1.5 T clinical scanner (Magnetom Vision, Siemens, Erlangen, FRG). Two independent neuroradiologists measured the thickness of the ligamenta flava in mm. Statistics included Pearson's correlation coefficient and the intra-class correlation coefficient. RESULTS: Mean values did not differ significantly. The correlation coefficients varied between 0.69 and 0.98. The best correlation occurred comparing the same techniques in different windowing and weighting (CT: r = 0.98; MRI: r = 0.95). Correlating different techniques the combination of CT bone window and T1 weighted images presented the best result (r = 0.75). CONCLUSIONS: Because of the excellent correlation between the examined techniques CT as well as MRI can equally be used to measure distances of spinal structures.