Lutz Arne Mueller

Ultrasound-guided spinal fracture repositioning, ligamentotaxis, and remodeling after thoracolumbar burst fractures.

Study Design. Computed tomography aided evaluation of spinal decompression by ultrasound-guided spinal fracture repositioning, ligamentotaxis, and remodeling after thoracolumbar burst fractures. Objectives. To determine the necessity of spinal canal widening by ultrasound-guided fracture repositioning for fractures with and without neurologic deficit. Summary of Background Data. Ultrasound-guided spinal fracture repositioning is an alternative new approach. Reports have varied concerning ligamentotaxis and remodeling. Methods. Computed tomography aided planimetry of the spinal canal (64 consecutive burst fractures) and neurologic evaluation by Frankel grades. Results. Ultrasound-guided spinal fracture repositioning (n = 37) reduced the stenosis of the spinal canal area from 45% before surgery to 20% after surgery of the estimated original area. Fifteen patients had a primary neurologic deficit, which improved markedly in 11 cases after treatment. Patients with neurologic symptoms had a greater preoperative spinal stenosis than those without. No correlation was seen between the degree of pretreatment spinal stenosis, fracture type, and severity of the neurologic deficit. Ligamentotaxis (n = 27) reduced the stenosis from 30% before surgery to 18% after surgery and remodeling (n = 11) from 25% after surgery to 13% after metal removal. Conclusion. Ultrasound-guided fracture repositioning is an efficient method for spinal canal decompression of burst fractures with neurologic symptoms. The marked degree of widening of the spinal canal due to the effects of ligamentotaxis and remodeling may render the reposition of retropulsed fragments unnecessary in cases of fractures without a neurologic deficit.

Periacetabular cortical and cancellous bone mineral density loss after press-fit cup fixation: a prospective 7-year follow-up.

The impact of total hip arthroplasty on strain adaptive bone remodeling has been extensively analyzed by dual-energy x-ray absorptiometry. In this study, we present a prospective computed tomography-assisted study of periacetabular cortical and cancellous bone mineral density (in milligrams of calcium hydroxyapatite [CaHA] per milliliter, or mgCaHA/mL) changes 10 days and 1, 3, and 7 years after press-fit cup implantation for 38 hips in vivo. Cancellous bone mineral density decreased by Ø -63% ventral and Ø -85% dorsal to the cup; cortical bone mineral density, by Ø -22% ventral and Ø -18% dorsal to the cup. The presented periacetabular strain adaptive bone mineral density data are the most extensive of the current literature. Even the measured extensive cancellous bone mineral density loss was thus far of no clinical relevance because all cups showed radiographic signs of stable ingrowth.

Use of orthoses and orthopaedic technical devices in proximal spinal muscular atrophy. Results of survey in 194 SMA patients

Purpose. The purpose of this study is to determine the use of orthopaedic and assistive devices for Spinal muscular atrophy (SMA) patients, following a survey of 194 patients. Method. The use of wheelchairs, corsets and orthoses was evaluated in 194 SMA patients whose mean age was 12.6 (SD 7.2, 0.7–41.1). There were 14 patients with SMA type Ib (age range 1.7–36.9), 133 with type II (age range 0.7–37.7), 42 with type IIIa (age range 3.2–41.1) and 5 with type IIIb (age range 8.0–20.0). Results. One hundred and sixteen patients (60%) had powered and 29 patients (15%) manual wheelchairs. Nineteen patients (10%) used long leg orthoses. Ten patients (5%) used swivel walkers and 26 (13%) had standing frames. Twenty-six patients (13%) received lower leg orthoses because of foot deformities. Eight patients (4%) used night splints for the lower limbs. One hundred and fifteen patients (59%) were fitted with corsets because of progressive scoliosis. Conclusion. This is the first study about the provision of orthopaedic and assistive devices in a large group of SMA patients. Following the results of this survey we can optimise the strategy of providing orthoses and assistive devices for SMA patients and better adapt them to the patients individual needs.

Dynamische Analyse von Osteosynthesen am Olecranon: ein in-vitro Vergleich zweier Osteosynthesesysteme / Dynamic analysis of olecranon osteosyntheses – an in vitro comparison of two osteosynthesis systems

Zusammenfassung Hintergrund: Ziel dieser Studie war die Entwicklung eines Test-Setups mit kontinuierlicher Winkeländerung für die Imitation der Gelenkbewegung des Ellenbogens zum mechanischen Vergleich von Zuggurtungosteosynthese und einem neu entwickelten intramedullären Nagelsystem. Material und Methode: Der Rotationsmotor des servopneumatischen Testapparates arbeitet winkelgesteuert für die Ellenbogenbewegung, der Linearmotor kraftgesteuert für den M. triceps brachii. Das Frakturmodell wurde dynamisch unter zyklischer Belastung getestet. An 14 frischen Leichenulnae wurde eine schräge Osteotomie des Olecranon durchgeführt und zwei verschiedene Osteosynthesesysteme angelegt. Eine Gruppe erhielt die Zuggurtungsosteosynthese, die andere Gruppe den intramedullären Nagel implantiert. Das Bewegungsausmaß des Ellenbogengelenkes änderte sich zwischen 0° Extension und 100° Flexion unter einer dynamischen Zugkraftvariation zwischen 25 und 150 N. Anhand zweier Paare von Markerpins, die jeweils am proximalen und am distalen Fragment frakturnah angebracht waren, wurde die Relativbewegung zwischen den Pins gemessen. Die Bewegungsanalyse wurde nach 4 und nach 300 Zyklen kontinuierlicher Belastung durchgeführt. Ergebnisse: Nach 300 Zyklen war die Lockerung der Zuggurtungsosteosynthese signifikant höher als die der intramedullären Nagelosteosynthese. Diskussion: Andere Untersuchungen von Osteosynthesen mit Gelenkbeteiligung veränderten die Krafteinwirkung nicht dynamisch. Das Test-Setup der vorliegenden Studie imitiert die Gelenkbewegung mit einer kontinuierlichen Änderung des Gelenkwinkels. Das ist eine wichtige Voraussetzung für eine akkurate biomechanische Untersuchung von unterschiedlichen Osteosyntheseverfahren zur Fixierung von Olecranonfrakturen. Das getestete intramedulläre Nagelsystem zeigte im Vergleich zur Zuggurtungsosteosynthese eine signifikant geringere Lockerung unter Belastung. Abstract Introduction: The aim of the present study was to develop a test setup with continuous angle alteration to imitate elbow joint motion for the mechanical evaluation of tension band wiring and a newly designed intramedullary nail. Materials and methods: The servo-pneumatical test stand worked with a rotational angle-adjusted and a linear force-adjusted engine. The fracture model was dynamically tested under cyclic loading imitating elbow joint motion. In total, 14 fresh cadaver upper extremities underwent olecranon fracture by means of transverse osteotomy and were assigned to two groups: tension band wiring and intramedullary nailing. There was a continuous angle alteration between 0 and 100° of flexion, with continuous changing pull force between 25 N and 150 N. Two steel pins were placed in the proximal, two in the distal olecranon fragment for video analysis of the motion between the two pairs of pins. Displacement in the fracture gap was determined after 4 and 300 cycles. Results: After 300 cycles, the displacement in the fracture fixation model was significantly higher in the tension band wiring group than in the intramedullary nailing group. Discussion: Other studies evaluating biomechanical properties of olecranon osteosyntheses with joint involvement did not change the force direction dynamically. We introduced a test setup with continuous angle alteration to imitate joint motion. This is an important step for accurate biomechanical evaluation of the treatment of different fixation methods in olecranon fractures. The tested nailing system showed significant advantages in loosening under cyclic loading compared to tension band wiring.

Radiostereometric migration analysis of the Lubinus SP II hip stem: 59 hips followed for 2 years.

Abstract The aim of this prospective study was to analyze the migration pattern of the Lubinus SP II hip stem and to evaluate the clinical results. Fifty-nine patients were followed for 2 years. Translational and rotational micromotion of the implant was measured by radiostereometric analysis (RSA) and the Harris hip score (HHS), and the Charnley classification was used to assess the clinical outcome. Although there was a very small, but statistically significant, distal migration of 0.04±0.83 mm, the prosthesis was found stable at 2 years of follow-up. The main migration in this direction took place between 6 months and 1 year. Maximum total point motion (MTPM) showed a mean of 0.99±0.69 mm. Good clinical outcome with HHS results of 42±11 before and 79±16 at 2 years after surgery was observed. The Charnley classification showed increasing additional impairments in the 2-year interval, which is likely to influence the HHS results of future follow-ups. The migration values measured in the present study are far below the thresholds considered clinically relevant in literature. Thus, the conclusion can be drawn that the implant is not at risk for early aseptic loosening. Long-term RSA is required to assess possible late migration.

Hypothenar Hammer Syndrome in a Golf Player

The hypothenar hammer syndrome was first described by von Rosen in 1934 in a factory worker who struck the edge of a metal bar with the palm of his right hand in an attempt to loosen a tightly fixed screw. The factory worker experienced repetitive ischemia and pain attacks in all his digits. At surgery, von Rosen found a 2.5-cm thrombosed segment of the distal ulnar artery overlying the hamate bone. Since this first description, repetitive blunt or single severe trauma leading to thrombus formation of the ulnar artery and hand ischemia related to occupational exposure in patients who use vibrating hand tools or who hammer objects with the hypothenar aspect is well known. Such injury may also be seen in sports where the athlete’s hand is subjected to repeated or single severe impact. A review of the literature revealed 12 different sports that have been associated with hypothenar hammer syndrome (Table 1). This is the first report of a golf player who sustained traumatic ulnar artery thrombosis in a setting of repetitive swinging of a golf club.

Comparison of cortical and cancellous bone remodeling of the pelvis after press-fit cup total hip arthroplasty dependent on patient and prosthesis-specific characteristics: a computed tomography-assisted osteodensitometry study in vivo

Abstract Even though periprosthetic bone loss is common after total hip arthroplasty, there is no scientific evidence whether it compromises the survival of the prosthesis. Using quantitative computed tomography-assisted osteodensitometry, we determined the pattern of periacetabular bone density (BD) changes of two different press-fit cups (54 hips) 10 days, 1 year and 3 years post-operatively. We measured cortical and cancellous BD at three points of time and evaluated the effects of patient-specific characteristics [age, gender, body mass index (BMI)], clinical function, and BD at index operation. Cancellous BD decreased in all periacetabular regions by up to -52% (p≤0.001). In contrast, cortical BD above the dome of the cup remained constant while at the level of the cup it decreased by up to -17% (p≤0.001). Older patients had significantly lower cortical (ventral and dorsal) and cancellous (cranial) BD values, obese patients had a higher cortical BD ventral, and patients with excellent clinical results had a higher cancellous BD ventral and dorsal to the cup. Changes in BD suggest high stress shielding of retroacetabular cancellous bone, while load is transmitted to cortical bone above the dome of the cup. Patient-specific characteristics were shown to affect BD, but long-term analysis is needed to show whether these effects are of clinical importance.

Radiostereometric migration measurement of an uncemented Cerafit® femoral stem: 26 patients followed for 10 years

Abstract Radiostereometric analysis (RSA) is the gold standard for evaluating micromotions of orthopaedic implants. The method is applied for identifying novel design weaknesses in endoprostheses. Current research frequently assesses relatively short time periods. Short-term RSA studies have been widely used for predicting the long-term stability of many hip prosthetic designs, but only a few studies have focused on uncemented hip implants, especially for extended periods. The purpose of this study was to analyse the migration pattern of the Cerafit® femoral stem within 10 years and to verify the predictive value of short-term RSA after 2 years for this uncemented femoral hip stem. Twenty-six patients were followed for 10 years. Ten years after implantation, a mean subsidence of 0.22 mm±0.56 mm, a mean internal rotation of 0.59°±1.67° and a mean maximum total point motion (MTPM) of 1.28 mm±0.54 mm were detected. The main migration took place in the first 6 weeks after surgery (subsidence of 0.36 mm±0.73 mm; internal rotation of 0.62°±1.49°, MTPM of 1.05 mm±0.68 mm). All the migration values measured were small. No late-onset migration was observed. This study suggests that the Cerafit® implants are stable after 10 years. Thus, RSA could be the best tool to assess long-term implant behaviour.