Introduction: Diaphyseal fracture at a cortical perforation is the commonest postoperative complication of hips revised with impacted morsellised bone. To reduce fracture risk, surgeons can apply mesh, augment the bone with plate or strut graft, or bypass the perforation with a longer stem. No biomechanical data exists to choose between these alternatives. The objective of this study was to compare the above methods of cortical repair in terms of (i) bone fracture risk and (ii) stem migration.

Methods: Fourteen large composite femora (Sawbones, Malmö, Sweden) were prepared to simulate cavitary defects. An 18×40 mm lateral cortical perforation was made in 12 diaphyses. These diaphyses were repaired with mesh only, mesh and plate, or mesh and strut graft (n=4 each). Strut graft and plate were fixed with cables. Porcine cancellous bone was morsellised and impacted into each cavitary defect. Simplex P bone cement was injected. In the 12 femora with repaired perforation, a standard or a long Exeter prosthesis, bypassing the perforation 2 cortical diameters, was implanted. Thus, 6 methods of defect repair were created (mesh, plate and strut, combined with either long or short stem, each n=2). Standard stems impaction-grafted in the two femora without perforation served as control (n=2). Femora were placed in a testing machine and loaded at 1 Hz with 100 cycles of joint and abductor force. Peak joint force was 2,500 N. Strain amplitudes at the perforation and stem migration were determined. Statistical analysis was by 2-way and 1-way ANOVA, and the Student-Newman-Keuls (SNK) post-hoc test.

Results: Stem length did not affect average defect strain if used with plate or strut graft (2x2 ANOVA, p=0.62). Four combinations remained for further analysis: standard stem with mesh, long stem with mesh, plate, and strut graft, with defect strains of 5250, 3620, 2940, and 2480 μstrain. In controls, strains were 1750 μstrain. Defect strains differed significantly (ANOVA, p=0.0004), with strains for standard stems with mesh significantly higher than all other groups, those for long stems with mesh significantly higher than controls, and those for plate or strut graft no different from controls (SNK). Maximum permanent subsidence was 0.71 mm and retroversion 1.6°. For repaired perforations, stem length did not affect subsidence (p=0.96), but repair method did (p=0.03, both 2-way ANOVA). For further analysis, subsidence of the three repair methods (mesh, plate and strut graft with subsidence of 0.24, 0.47 and 0.19 mm, resp.) was compared with that of controls (0.52 mm). Subsidence differed significantly (ANOVA, p=0.02), and stems with strut graft subsided significantly less than those with plate or controls (SNK). Permanent retroversion was similar for each group.

Dicussion: Non-reinforced defects with a standard stem generated high defect strain amplitudes. A long stem bypassing the defect reduced these strains by 30%, and might suffice in case of otherwise strong cortex. In other cases, augmentation of the perforated diaphysis with either strut graft or plate needed to minimise fracture risk. Stem migration in reconstructed perforated diaphyses was always less than control cases, suggesting stem migration is no specific problem in reconstruction.

Introduction: Propionibacterium acnes (P. acnes), a common anaerobic skin commensal, has been implicated in biomaterial-related infections (BRI). Bacteria can adhere to biomaterial surfaces and grow as a bio-film held together by exopolymer, exhibiting increased antimicrobial resistance. To our knowledge, images of P. acnes biofilms have not previously been published. We have demonstrated the ability of P. acnes to adhere to surgical steel and to develop a biofilm on this material. However its ability to adhere to and develop a biofilm on titanium, a commonly used surgical implant material, has not been fully investigated.

Aims:

To determine the quantitative adherence and biofilm development of P. acnes on titanium compared to surgical steel.

Method: Six clinical isolates of P. acnes were assayed for adherence to materials with and without plasma glycoprotein conditioning film by chemiluminescence and culture. Biofilm development was assessed by chemiluminescence, fluorescence microscopy, environmental (ESEM) and scanning electron microscopy (SEM). Mature biofilms were exposed to plasma concentrations of penicillin and quantified by chemiluminescence and culture. Unpaired student’s t tests and univariate linear regression models were calculated using SPSS software (version 12).

Results: Univariate linear regression showed that P. acnes adherence to titanium was 18% (p=0.001) greater than to steel. Adherence was reduced by the presence of the conditioning film on titanium by 28% (p=0.001), but this made no significant difference to P. acnes adherence to steel. P. acnes biofilms were clearly demonstrated, along with bacterial expolymer, showing an interesting similarity to biofilms of S. epidermidis. P. acnes grows as a thick biofilm on both materials held together by exopolymer and our preliminary results suggest that biofilms on titanium might be less susceptible to antimicrobials after 24 hours of penicillin treatment; a reduction of 94% on steel and 81% on titanium (p=0.057, p=0.39 resp).

Conclusions: P. acnes adheres to steel and titanium, a crucial first step in BRI. Greater numbers of P. acnes adhere to titanium than to steel. The naked surface of titanium is microporous, assisting adhesion. A conditioning film reduces P. acnes adherence to titanium but not to steel. P. acnes develops as a biofilm on steel and titanium. Results indicate that pathogenesis of P. acnes infection on titanium is more successful than on steel. P. acnes biofilms on titanium may be harder to eradicate with antimicrobial agents.

The use of impaction bone grafting during revision arthroplasty of the hip in the presence of cortical defects has a high risk of post-operative fracture. Our laboratory study addressed the effect of extramedullary augmentation and length of femoral stem on the initial stability of the prosthesis and the risk of fracture.

Cortical defects in plastic femora were repaired using either surgical mesh without extramedullary augmentation, mesh with a strut graft or mesh with a plate. After bone impaction, standard or long-stem Exeter prostheses were inserted, which were tested by cyclical loading while measuring defect strain and migration of the stem.

Compared with standard stems without extramedullary augmentation, defect strains were 31% lower with longer stems, 43% lower with a plate and 50% lower with a strut graft. Combining extramedullary augmentation with a long stem showed little additional benefit (p = 0.67). The type of repair did not affect the initial stability. Our results support the use of impaction bone grafting and extramedullary augmentation of diaphyseal defects after mesh containment.

Purpose: Chondroblastomas are a lesion of immature cartilage found in a typically epiphyseal location. The peak incidence is in teenagers. Current surgical treatment is a balance between complete excision, with potential for physeal and articular cartilage damage, and local recurrence. A minimally invasive technique with a low complication rate providing effective treatment may be provided by radiofrequency (RF) thermocoagulation. Already the treatment of choice for Osteoid Osteoma – another lesion that can occur in the epiphysis.1,2,3 Literature to date on clinical use of RF thermocoagulation in chondroblastoma is scarce.4 The high water content of chondroblastoma should ensure its sensitivity to RF ablation. Our units experience in osteoid osteoma has been extended to RF thermocoagulation of chondroblastoma.

Patients: Four patients were treated with RF thermocoagulation for a chondroblastoma. Minimum follow up one year.

Methods: A RITA Starburst probe thermocoagulates the lesion for at least 5 minutes at 90 degrees centigrade. Overnight stay and outpatient follow up until skeletal mature, or two years following treatment.

Results: Two chondroblastomas were in the proximal tibia, one in the distal femur and one in the proximal humerus. One patient had surgery previously and one patient presented with collapse of the proximal tibial plateau. All patients were treated successfully and are pain free. All patients, accepting the one with pre-existing collapse, have a full range of movement. There has been no local recurrence at one year.

Conclusion & Discussion: Our experience suggests that radiofrequency thermocoagulation is a safe and effective treatment method for patients with chondroblastoma.

Carpal tunnel syndrome is the commonest nerve entrapment syndrome. There is still controversy over the method of anaesthesia for this procedure. There have been many studies to show the effectiveness of local infiltration anaesthesia. However, patients do not always tolerate it, as one of the disadvantages of local anaesthetic is pain on infiltration. Experimental studies have shown that warming local anaesthetic can reduce the pain of injection in normal subjects. The aim of our study is to assess the effect of warming local anaesthetic for carpal tunnel surgery.

We conducted a prospective randomised controlled trial. Sample size was calculated. The study group consisted of patients undergoing carpal tunnel surgery. The treatment group received local anaesthetic at 37°C, the control group at room temperature. Patients were asked to indicate the degree of discomfort on a visual analogue scale (0 to 100).

There was a significant reduction in pain scores in the treatment group. Warming the local anaesthetic produced a mean visual analogue score of 13.8 versus 43 for the control group. These results were statistically significant (p< 0.05).

Many carpal tunnel releases are performed under General Anaesthetic . One of the main reasons cited was poor patient tolerance to local anaesthetic infiltration due to pain. Our results show a significant reduction in the reported pain by warming the local anaesthetic for carpal tunnel release. We suggest that warming local anaesthetic should be best practice for anaesthesia in carpal tunnel release.