Sebastian Radmer

Total wrist arthroplasty in patients with rheumatoid arthritis

PURPOSE After very good midterm results with an uncemented total wrist arthroplasty we evaluated the long-term outcome in a retrospective study. METHODS Forty uncemented anatomic physiologic (APH, Implant-Service Vertreibs-GmbH, Hamburg, Germany) wrist prosthesis implantations performed in 40 patients were reviewed. The mean follow-up period was 52 months (range, 24-73 mo) and the following parameters were examined: radiographs, grip strength, range of motion, and patients satisfaction. RESULTS After a good short-term outcome the results deteriorated with time. The following complications occurred: 2 infections, 3 implant failures, 2 prosthesis migrations, and 33 loosenings/dislocations. All patients (39 of 40) underwent revision surgery, and severe titanium wear in the soft tissues was found intraoperatively in all cases. It became clear that even in a non-weight-bearing joint such as the wrist, titanium alloy may wear and result in tissue metallosis when used as a bearing surface of the implant. As a salvage procedure the prosthesis was removed and an arthrodesis was performed in all patients. CONCLUSIONS Because of the deterioration of the results including an unacceptable revision rate we currently do not consider the anatomic physiologic wrist prosthesis to be a suitable implant in patients with rheumatoid arthritis.

Imaging of hamate bone fractures in conventional X-rays and high-resolution computed tomography. An in vitro study.

RATIONALE AND OBJECTIVES To examine the ability to image fractures of the body and hook of the hamate bone in conventional X-rays and high-resolution computed tomography (HR-CT). MATERIALS AND METHODS In an in vitro experiment using 18 cadaver hands, the hamate bone was fractured at different places. Before and after fracture, conventional X-rays were taken in different planes (anteroposterior, lateral, oblique, and carpal tunnel), and HR-CT was performed with 2-mm layer thickness in the axial, sagittal, and coronal plane. RESULTS Taking into account all the conventional X-ray projections applied, the in vivo experiment revealed a sensitivity of 72.2%, a specificity of 88.8%, and an accuracy of 80.5%. For the HR-CT, the sensitivity was 100%, the specificity was 94.4%, and the accuracy was 97.2%. CONCLUSIONS Fractures of the body and hook of the hamate cannot always be detected with certainty in the conventional X-ray image, even if different projectional planes are used. The HR-CT is the imaging procedure of choice for further clarification, and an axial or sagittal plane should be selected.

Computed tomography for preoperative planning in minimal-invasive total hip arthroplasty: radiation exposure and cost analysis.

Computed tomography (CT) was used for preoperative planning of minimal-invasive total hip arthroplasty (THA). 92 patients (50 males, 42 females, mean age 59.5 years) with a mean body-mass-index (BMI) of 26.5 kg/m(2) underwent 64-slice CT to depict the pelvis, the knee and the ankle in three independent acquisitions using combined x-, y-, and z-axis tube current modulation. Arthroplasty planning was performed using 3D-Hip Plan(®) (Symbios, Switzerland) and patient radiation dose exposure was determined. The effects of BMI, gender, and contralateral THA on the effective dose were evaluated by an analysis-of-variance. A process-cost-analysis from the hospital perspective was done. All CT examinations were of sufficient image quality for 3D-THA planning. A mean effective dose of 4.0 mSv (SD 0.9 mSv) modeled by the BMI (p<0.0001) was calculated. The presence of a contralateral THA (9/92 patients; p=0.15) and the difference between males and females were not significant (p=0.08). Personnel involved were the radiologist (4 min), the surgeon (16 min), the radiographer (12 min), and administrative personnel (4 min). A CT operation time of 11 min and direct per-patient costs of 52.80 € were recorded. Preoperative CT for THA was associated with a slight and justifiable increase of radiation exposure in comparison to conventional radiographs and low per-patient costs.

Therapeutic alternatives in nonunion of hamate hook fractures : Personal experience in 8 patients and review of literature

Symptomatic nonunion frequently results after conservative treatment of hamate hook fractures, emphasizing the need of appropriate surgical strategies. A retrospective analysis of 8 patients with nonunions treated by fragment excision or open reduction and internal fixation (ORIF) at 3 centers was performed. The literature was reviewed for treatment options, as bone grafting and low-intensity pulsed ultrasound. Although fragment excision is advocated as the “gold standard” in nonunion, reports on functional results are controversial, and recent anatomic and biomechanical studies of the hook challenge this opinion. In our patients, complete relief of symptoms and comparable functional results were observed after ORIF or fragment excision. Bone grafting could supplement ORIF in selected cases. Low-intensity pulsed ultrasound may evolve as a conservative treatment option. Several alternatives to hook excision are available aiming at complete anatomic and functional recovery of hamate hook nonunion. Further experience is needed before general recommendations can be formulated.

Computed tomography for preoperative planning in total hip arthroplasty: what radiologists need to know.

The number of total hip arthroplasties is continuously rising. Although less invasive surgical techniques, sophisticated component design, and intraoperative navigation techniques have been introduced, the rate of peri- and postoperative complications, including dislocations, fractures, nerve palsies, and infections, is still a major clinical problem. Better patient outcome, faster recovery and rehabilitation, and shorter operation times therefore remain to be accomplished. A promising strategy is to use minimally invasive techniques in conjunction with modular implants, aimed at independently reconstructing femoral offset and leg length on the basis of highly accurate preoperative planning. Plain radiographs have clear limitations for the correct estimation of hip joint geometry and bone quality. Three-dimensional assessment based on computed tomography (CT) allows optimizing the choice and positions of implants and anticipating difficulties to be encountered during surgery. Postoperative CT is used to monitor operative translation and plays a role in arthroplastic quality management. Radiologists should be familiar with the needs of orthopedic surgeons in terms of CT acquisition, post-processing, and data transfer. The CT protocol should be optimized to enhance image quality and reduce radiation exposure. When dedicated orthopedic CT protocols and state-of-the-art scanner hardware are used, radiation exposure can be decreased to a level just marginally higher than that of conventional preoperative radiography. Surgeons and radiologists should use similar terminology to avoid misunderstanding and inaccuracies in the transfer of preoperative planning.

DORSAL PERCUTANEOUS CANNULATED MINI-SCREW FIXATION FOR FRACTURES OF THE HAMATE HOOK

PURPOSE Open fixation of acute fractures, delayed union and non-union of the hamate hook through a palmar approach has been reported. Minimal invasive fixation using a dorsal percutaneous approach and a headless cannulated mini-screw is another option not commonly considered. The authors present their case series of patients who underwent dorsal percutaneous fixation of acute fractures and delayed union of the hamate hook. METHODS This study retrospectively reviewed six consecutive patients (five male patients and one female patient) with non-displaced acute fractures (< 8 weeks) and delayed union (8 to 12 weeks) of the hamate hook treated with dorsal percutaneous cannulated mini-screw fixation. The indications for surgery included wrist pain, patient refusal of conservative treatment, and prevention of non-union and hook excision. Exclusion criteria included displacement or inadequate size of the hamate hook, previous surgery, associated carpal injury, flexor tendon rupture, and median or ulnar nerve lesion in the carpal tunnel and Guyons canal respectively. Each fracture was visualized by radiography and computed tomography before and after the intervention. RESULTS Anatomically correct fixation of the hamate hook with central screw positioning was achieved in all patients. No displacement or disruption of the cortical shell of the hook was observed. The union rate was 100% with all patients being able to resume their pre-injury activities after an average of seven weeks from surgery. CONCLUSIONS This pilot study demonstrates that non-displaced acute fractures and delayed union of the hamate hook can be treated successfully by dorsal percutaneous cannulated mini-screw fixation with minimal morbidity and complications.

Poor experience with a hinged endoprosthesis (WEKO) for the metacarpophalangeal joints: All 28 prostheses removed within 2 years in 8 patients having rheumatoid arthritis

We prospectively assessed the outcome of implanting a hinged prosthesis in destroyed metacarpophalangeal (MCP) joints (Larsen stage III-V). We implanted 28 cementless, axis-coupled total endoprostheses with hinging (WEKO prosthesis, Implant-Service GmbH, Hamburg, Germany) in 8 women (mean age 62 (47-80) years) suffering from rheumatoid arthritis. The mean follow-up period was 15 (12-18) months, and the evaluation was based on objective criteria, including joint motion, ulnar deviation of the long fingers, grip strength, radiographic migration and torsion of the prostheses, as well as the patients´ subjective satisfaction. 12 months postoperatively, the mean arc of flexion was 30 (22-35)°, and the mean extension lag was 43 (40-48)°. Although no ulnar deviation was seen in 2 fingers, it was <10° in 3, between 10° and 20° in 7 of the fingers, and more than 20° in 16. None of the patients could clench their fist firmly. We found prosthesis migration in 20 and torsion in 19 fingers. 2 years postoperatively, we had to remove all of the prostheses due to functional failure.

MR Diagnosis of Retropatellar Chondral Lesions under Compression A Comparison with Histological Findings

Purpose: The aim of the study was to improve the chondromalacia patellae (CMP) diagnosis by MR imaging under defined compression of the retropatellar cartilage, using a specially designed knee compressor. The results were compared with histological findings to obtain an MR classification of CMP. Method: MR imaging was performed in in vitro studies of 25 knees from cadavers to investigate the effects of compression on the retropatellar articular cartilage. The results were verified by subsequent histological evaluation. Results: There was a significant difference in cartilage thickness reduction and signal intensity behaviour under compression according to the stage of CMP. Conclusion: Based on the decrease in cartilage thickness, signal intensity behaviour under compression, and cartilage morphology, the studies permitted an MR classification of CMP into stages I—IV in line with the histological findings. Healthy cartilage was clearly distinguished, a finding which may optimize CMP diagnosis.

HIGH INCIDENCE OF HAMATE HOOK FRACTURES IN UNDERWATER RUGBY PLAYERS: DIAGNOSTIC AND THERAPEUTIC IMPLICATIONS

Hamate hook fractures are rare injuries but appear to occur frequently in underwater rugby, the reason for which was investigated in this study. High-level underwater rugby players with hook fractures diagnosed during a five-year interval (2005-2010) were studied retrospectively. Medical data on these patients were reviewed for information on the mechanism of injury, type of fracture, radiological imaging, treatment, and outcome. In ten patients, hook fractures of the leading hand were confirmed by computed tomography, all of which were associated with specific injuries during underwater rugby games. Conservative treatment resulted in delayed healing or non-union, wherefore fragment excision and open reduction and internal fixation was performed in ten and five patients, respectively, while two patients declined surgery. After surgery, all patients were able to play underwater rugby again. In underwater rugby, hook fractures occur frequently due to high and repeated forces applied to the leading hand during games.

Minimal Invasive Fixation of Hamate Hook Fractures Through a Dorsal Percutaneous Approach Using a Mini Compression Screw: An Experimental Feasibility Study

Purpose:Isolated fractures of the hamate hook can be treated by conservative or surgical means. Because nonoperative treatment is associated with high nonunion rates, surgical treatment with open reduction and internal fixation through a palmar approach is often preferred. The aim of this study was to refine surgical treatment of hamate hook fractures using a cannulated mini compression screw through a dorsal percutaneous approach.Methods:Artificial fractures of the hamate hook were created in five male cadaver hands under fluoroscopy. Using an ulnar approach, the hamate hook was fractured at the base (n = 3) and middle third (n = 2) of the hook using an osteotome. Each fracture was visualized by X-ray and computed tomography. Under fluoroscopy, the fracture was stabilized with a 1.1 mm K wire through a dorsal percutaneous approach which guided the introduction of a 3 mm diameter cannulated mini compression screw. The screw position was then controlled by X-ray and computed tomography.Results:Percutaneous fixation of the fractured hook through the dorsal approach was achieved in all cases. Regardless of the fracture location, all fragments were adapted into anatomically correct positions. No displacement or disruption of the cortex of the hook was observed with central screw positioning.Conclusion:Minimal invasive repair of isolated hamate hook fractures through a dorsal percutaneous approach is feasible. The special properties of the cannulated mini compression screw allow optimal screw positioning and stable fixation without risk of diplacement or disruption of the hook fragment.