Capsule repair may reduce dislocation following hip hemiarthroplasty through a direct lateral approach: a cadaver study.

Reported rates of dislocation in hip hemiarthroplasty (HA) for the treatment of intra-capsular fractures of the hip, range between 1% and 10%. HA is frequently performed through a direct lateral surgical approach. The aim of this study is to determine the contribution of the anterior capsule to the stability of a cemented HA through a direct lateral approach. A total of five whole-body cadavers were thawed at room temperature, providing ten hip joints for investigation. A Thompson HA was cemented in place via a direct lateral approach. The cadavers were then positioned supine, both knee joints were disarticulated and a digital torque wrench was attached to the femur using a circular frame with three half pins. The wrench applied an external rotation force with the hip in extension to allow the hip to dislocate anteriorly. Each hip was dislocated twice; once with a capsular repair and once without repairing the capsule. Stratified sampling ensured the order in which this was performed was alternated for the paired hips on each cadaver. Comparing peak torque force in hips with the capsule repaired and peak torque force in hips without repair of the capsule, revealed a significant difference between the 'capsule repaired' (mean 22.96 Nm, standard deviation (sd) 4.61) and the 'capsule not repaired' group (mean 5.6 Nm, sd 2.81) (p < 0.001). Capsular repair may help reduce the risk of hip dislocation following HA.

Bearing exchange in the management of pseudotumours.

INTRODUCTION: Soft tissue reactions following metal-on-metal (MoM) arthroplasty of the hip have been under considerable discussion. These reactions are seen following both hip resurfacing and MoM total hip arthroplasty (THA). The phenomenon may arise owing to shedding of metal particles in high wear states, hypersensitivity with normal metal wear rates or a combination of the two. METHODS: Three patients were identified who had developed a soft tissue reaction (pseudotumour) following MoM hip resurfacing procedures. The prostheses were revised to ceramic-on-ceramic (CoC) THA with only minimal debridement of the pseudotumour. Pre and postoperative magnetic resonance imaging was performed to assess the size of the lesions. RESULTS: Progressive and satisfactory resolution of the associated pseudotumours was identified following revision of the prostheses to CoC THA. CONCLUSIONS: In the early stages of pseudotumour formation following MoM hip resurfacing, this potentially devastating condition can be managed adequately with revision to a CoC bearing THA with minimal soft tissue excision.

A study of microbial colonisation of orthopaedic tourniquets.

INTRODUCTION: Tourniquets are employed widely in orthopaedic surgery. The use of the same tourniquet on a repetitive basis without a standard protocol for cleaning may be a source of cross-infection. This study examines the contamination of the tourniquets in our institution. MATERIALS AND METHODS: Agar plates were used to take samples from 20 tourniquets employed in orthopaedic procedures. Four sites on each tourniquet were cultured and incubated at 37 degrees C for 48 h. RESULTS: All sampled tourniquets were contaminated with colony counts varying from 9 to > 385. Coagulase-negative Staphylococcus spp. were the most commonly grown organisms from the tourniquets (96%). Some tourniquets had growths of important pathogens including methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas spp., and S. aureus. On cleaning five tourniquets with Clinell (detergent and disinfectant) wipes (GAMA Healthcare Ltd, London, UK), there was a 99.2% reduction in contamination of the tourniquets 5 min after cleaning. CONCLUSIONS: In addition to the manufacturers' guidelines, we recommend the cleaning of tourniquets with a disinfectant wipe before every case.

The role of polymethylmethacrylate bone cement in modern orthopaedic surgery.

Polymethylmethacrylate remains one of the most enduring materials in orthopaedic surgery. It has a central role in the success of total joint replacement and is also used in newer techniques such as percutaneous vertebroplasty and kyphoplasty. This article describes the current uses and limitations of polymethylmethacrylate in orthopaedic surgery. It focuses on its mechanical and chemical properties and links these to its clinical performance. The behaviour of antibiotic-loaded bone cement are discussed, together with areas of research that are now shedding light upon the behaviour of this unique biomaterial.

The effect of surgical approach on blood flow to the femoral head during resurfacing.

We determined the effect of the surgical approach on perfusion of the femoral head during hip resurfacing arthroplasty by measuring the concentration of cefuroxime in bone samples from the femoral head. A total of 20 operations were performed through either a transgluteal or an extended posterolateral approach. The concentration of cefuroxime in bone was significantly greater when using the transgluteal approach (mean 15.7 mg/kg; 95% confidence interval 12.3 to 19.1) compared with that using the posterolateral approach (mean 5.6 mg/kg; 95% confidence interval 3.5 to 7.8; p < 0.001). In one patient, who had the operation through a posterolateral approach, cefuroxime was undetectable. Using cefuroxime as an indirect measure of blood flow, the posterolateral approach was found to be associated with a significant reduction in the blood supply to the femoral head during resurfacing arthroplasty compared with the transgluteal approach.

Accuracy of femoral templating in reproducing anatomical femoral offset in total hip replacement.

Restoration of hip biomechanics is a crucial component of successful total hip replacement. Preoperative templating is recommended to ensure that the size and orientation of implants is optimised. We studied how closely natural femoral offset could be reproduced using the manufacturers' templates for 10 femoral stems in common use in the UK. A series of 23 consecutive preoperative radiographs from patients who had undergone unilateral total hip replacement for unilateral osteoarthritis of the hip was employed. The change in offset between the templated position of the best-fitting template and the anatomical centre of the hip was measured. The templates were then ranked according to their ability to reproduce the normal anatomical offset. The most accurate was the CPS-Plus (Root Mean Square Error 2.0 mm) followed in rank order by: C stem (2.16), CPT (2.40), Exeter (3.23), Stanmore (3.28), Charnley (3.65), Corail (3.72), ABG II (4.30), Furlong HAC (5.08) and Furlong modular (7.14). A similar pattern of results was achieved when the standard error of variability of offset was analysed. We observed a wide variation in the ability of the femoral prosthesis templates to reproduce normal femoral offset. This variation was independent of the seniority of the observer. The templates of modern polished tapered stems with high modularity were best able to reproduce femoral offset. The current move towards digitisation of X-rays may offer manufacturers an opportunity to improve template designs in certain instances, and to develop appropriate computer software.

Should we use a separate knife for the skin?

The aim of this study was to re-assess whether the use of a 'one-knife technique' can be considered as safe as the alternative practice of using separate skin and inside knives for elective orthopaedic surgery. A total of 609 knife blades from 203 elective orthopaedic operations, with equal numbers of skin, inside and control blades, were cultured using direct and enrichment media. We found 31 skin blades (15.3%), 22 inside blades (10.8%), and 13 control blades (6.4%) gave bacterial growth. Of the 31 contaminated skin blades only three (9.7%) had growth of the same organism as found on the corresponding inside blade. It is not known whether contamination of deeper layers in the remaining 90% was prevented by changing the knife after the skin incision. The organisms cultured were predominantly coagulase-negative staphylococci and proprionibacterium species; both are known to be the major culprits in peri-prosthetic infection. Our study suggests that the use of separate skin and inside knives should be maintained as good medical practice, since the cost of a single deep infection in human and financial terms can be considerable.

Extracting the tip of a fractured DHS wire from the hip joint.

Dynamic Hip Screw fixation is a very commonly performed operation, but one not without complications (1-3). To stabilise the fixation the guide wire can be advanced into the subchondral bone. An unusual complication of this, and one not previously documented in the literature, is that the tip of the guide wire can fracture. We describe a simple method of removing the tip of the guide wire.

C reactive protein and skin temperature post total knee replacement.

We prospectively assessed 20 patients following uncomplicated total knee replacement (TKR). Clinical status, skin temperature and C-reactive protein (CRP) were measured preoperatively and at intervals up to 18 weeks. The CRP rose postoperatively up to 5-7 days but returned to normal values by 6 weeks. The skin temperature remained elevated up to 18 weeks. We concluded that in uncomplicated cases, the CRP should be within normal limits by 6 weeks after operation, but skin temperature may remain elevated up to 18 weeks. A sustained rise in these values may indicate the development of a complication such as infection and the patient must be closely monitored.

Methotrexate in the management of immune mediated cochleovesitibular disorders: clinical experience with 53 patients.

OBJECTIVE: To describe our experience with low dose weekly methotrexate (MTX) in the management of immune mediated cochleovestibular disorder (IMCVD). METHODS: Between 1991 and 1999, we treated 53 patients with IMCVD with MTX. Patients were selected on the basis of progressive vestibular symptoms that had responded to corticosteroids and in most cases, relapsed. MTX was initiated at a dose of 7.5 mg weekly and increased to doses up to 25 mg weekly as needed. Response was assessed by audiologic studies and history of change in tinnitus and vertigo. MTX was discontinued after 4-6 mo in patients showing no improvement, and after 12-18 mo in patients with improved and stable symptoms. RESULTS: Three patients were still in early therapy and had not improved. Of the 50 remaining patients, significant improvement was seen in vertigo in 27/39 (69%) patients, hearing loss in 25/47 (53%), and tinnitus in 11/42 (26%). Overall improvement in symptoms was seen in 35/50 (70%) patients. Four patients stopped MTX due to toxicity, and 11 due to lack of response. In 28 patients, MTX was stopped after 12-18 mo when symptoms had stabilized, and restarted in 5 of these after relapse. Seven patients remain on therapy with improved and stable symptoms after 17.3 mo. CONCLUSION: In this open label experience, a majority of patients with IMCVD improved with weekly low dose MTX therapy with minimal toxicity.

Low-dose oral methotrexate management of patients with bilateral Ménière's disease.

In this retrospective clinical trial, we evaluated the effectiveness of low-dose oral methotrexate in the management of bilateral Ménière's disease of immune-mediated origin. At our tertiary-care referral center, we evaluated ten men and eight women who had longstanding bilateral Ménière's disease that had been unresponsive to traditional conservative medical management. Sixteen of these patients had steroid-responsive bilateral Ménière's disease. Two patients had contraindications to steroids, but their clinical and laboratory evaluations were consistent with an immune-mediated process. Patients were treated with 7.5 to 20 mg/week of oral methotrexate. The mean duration of treatment was 16.7 months (range: 8 to 35), with a mean followup of 2 years (range: 9 mo to 5 yr). Changes in clinical symptoms (vertigo, hearing loss, tinnitus, and aural fullness), audiometric changes, and side effects of therapy were evaluated. Vertigo resolved in 14 patients (78%), was substantially alleviated in three patients (17%), and remained unchanged in one patient (6%). Hearing improved in five patients (28%) and stabilized in seven patients (39%). Tinnitus and aural fullness resolved or was relieved in 11 of 17 (65%) and 13 of 14 (93%) patients, respectively. Side effects were minimal and reversible. We conclude that low-dose oral methotrexate is effective and safe for treating bilateral Ménière's disease of immune-mediated origin. In this study, methotrexate alleviated vertiginous symptoms and improved or stabilized hearing in most patients. Low-dose methotrexate can be considered for patients with immune-mediated bilateral Ménière's disease when long-term treatment is required or when a steroid or cyclophosphamide is contraindicated.

Abducens internuclear and ascending tract of Deiters inputs to medial rectus motoneurons in the cat oculomotor nucleus: neurotransmitters.

The abducens internuclear and ascending tract of Deiters (ATD) pathways are the principal excitatory inputs to medial rectus motoneurons in the oculomotor nucleus and are related to the control of conjugate horizontal eye movements. Differences in the morphology and soma-dendritic distribution of abducens internuclear and ATD synaptic endings are correlated with known differences in the physiological properties of these independent inputs. The present study extends these observations to the ultrastructural localization of the excitatory amino acid neurotransmitters, glutamate and aspartate, using a postembedding immunogold procedure combined with the pre-embedding immunoperoxidase localization of anterogradely transported biocytin from the abducens nucleus and the ventral lateral vestibular nucleus. Consistent with their spheroidal synaptic vesicle content and the asymmetric pre/postsynaptic membrane profile, both the abducens internuclear and ATD synaptic endings are labeled with glutamate and aspartate. However, quantitative analysis of the density of colloidal gold particles associated with mitochondria versus synaptic vesicles/axoplasmic matrix reveals significant differences in the metabolic versus neurotransmitter pools of the amino acids in the two populations of synaptic endings. The findings indicate that both aspartate and glutamate, possibly co-localized, are the excitatory neurotransmitters utilized by abducens internuclear synaptic endings whose burst-tonic physiological activity conveys information related to eye position to medial rectus motoneurons. By contrast, glutamate is the excitatory neurotransmitter associated with ATD synaptic endings whose high frequency burst activity is related to head velocity.

Abducens internuclear and ascending tract of deiters inputs to medial rectus motoneurons in the cat oculomotor nucleus: synaptic organization.

Abducens internuclear and ascending tract of Deiters (ATD) inputs to medial rectus motoneurons in the oculomotor nucleus are important for conjugate horizontal movements. In the present study, the organization of these separate populations of neurons and their synaptic connections with medial rectus motoneurons in the cat oculomotor nucleus have been examined by light and electron microscopy by using retrograde and anterograde axonal tracers. Consistent with the patterns of retrograde horseradish peroxidase labeling, the abducens internuclear projection is predominantly, if not exclusively, contralateral, whereas the ATD projection is exclusively ipsilateral, as demonstrated by anterograde autoradiographic and biocytin labeling. Both populations of synaptic endings contain spheroidal synaptic vesicles and establish synaptic contacts with modest postsynaptic densifications. In addition, ATD synaptic endings frequently are associated with subjunctional dense bodies and subsurface cisternae. The two populations of excitatory inputs differ, however, in their soma-dendritic distribution. The majority of abducens internuclear synaptic endings contact distal dendrites, whereas the majority of ATD synaptic endings contact proximal dendrites or somata. Abducens internuclear synaptic endings furthermore have a higher density of mitochondria than ATD synaptic endings. The more proximal location of ATD synaptic endings is consistent with the faster rise time and earlier reversal to polarizing currents of ATD excitatory postsynaptic potentials in comparison to those evoked by the abducens internuclear pathway as determined electrophysiologically. Given the differences in the physiologic signals conveyed by the abducens internuclear (eye velocity and eye position) and ATD (head velocity) pathways, the findings in this study suggest that the soma-dendritic stratification of the two inputs to medial rectus motoneurons may provide a means for the separate control of visuomotor and vestibular functions, respectively.

Gentamicin release from old cement during revision hip arthroplasty.

Bone cement containing gentamicin may release antibiotic when fractured during revision operations. Tissue samples taken during surgery may be contaminated by gentamicin and give inaccurate microbiological assessment. We studied five patients in whom cement containing gentamicin had been used in the primary procedure. During revision hip replacement, samples of joint fluid, tissues and cement were taken both before and after disruption of the cement. With the exception of one sample of joint fluid, low concentrations of gentamicin were recorded in the samples taken before the cement was disrupted, but after disruption the specimens contained gentamicin at concentrations high enough to inhibit or prevent growth of sensitive organisms. The cement contained very high levels up to ten years after insertion. Our findings suggest that no reliance can be placed on the microbiological assessment of specimens taken once cement splitting has started and that specimens should therefore be taken as early as possible.