Introduction: Iontophoresis is a method to introduce antibiotic molecules into allograft bone using an electrical potential; the antibiotics may then be released at therapeutic levels for extended periods of time. This is the first report of iontophoresed allograft implantation into patients.

Method: A method of loading tubular sections of cortical bone was used in theatre prior to implantation. Postoperative serum, drain and allograft antibiotic assays were performed. Patients were followed-up clinically and radiologically. All patients who received a bulk segmental allograft from June 1997 were entered into the trial.

Results: Since June 1997, 35 patients have received 37 allografts. Indications for allograft insertion were limb salvage for tumour (18), and poor bone stock associated with infection (11), periprosthetic fracture (6), aseptic loosening (1) and recurrent dislocation of total hip replacement (1). Mean follow-up is 3.3 years, and no patients have been lost to follow-up. One patient received two allografts in different sites and one had an allograft exchange. There has been one superficial wound infection and one deep infection. The latter patient was revised to another iontophoresed allograft and has had no recurrence at 34 months. One allograft has been revised to a vascularised fibular graft and allograft exchange following fracture of metal fixation. There was one case of persistent non-union in a knee arthrodesis which was treated after 21 months by removal of the intramedullary fixation and use of an Illizarov frame. The allograft was not revised. All other allografts are in situ with no complications related to the allograft. Eleven patients had pre-existing proven infections. None of these patients have been re-infected to date. Therapeutic gentamicin and flucloxacillin levels were detected in drain fluid samples post-operatively.

Conclusions: Iontophoresis is a safe and inexpensive technique that delivers high local dose of antibiotic, which may reduce infection in avascular allograft bone.

Introduction We believe minimally invasive surgery should be defined by the extent of soft tissue dissection rather than incision length. We describe a new technique that is truly soft-tissue sparing and report our early results.

The surgical approach The landmarks for the incision are identified and a 6–8cm oblique incision is made over the posterior aspect of the greater trochanter. Longer incisions are required in more difficult cases. Piriformis and the proximal insertion of gluteus maximus are preserved. After implant insertion, meticulous capsular repair is performed through drill holes into bone to reconstruct the posterior envelope. There are no restrictions to mobility. No specialised instruments are required.

Method The standard posterior approach (group 1) was compared with the PSMI approach (group 2) in a prospective cohort study of 200 consecutive patients over 60 years of age. In the standard approach the external rrotators were dettached. The capsule was repaired to bone, and the piriformis tendon reattached to the Gluteus Medius tendon. Routine restrictions to mobility were imposed. Patients were scored pre-operatively and followed up prospectively, by a blinded observer.

Results Demographics and functional scores were similar. Mean operation time was about 1 hour in both groups. Mean incision length was 21.5 cm (range 15 – 25) in group 1 and 8.4 cm (range 6 – 16) in group 2. Mean blood loss in group 1 was significantly higher than group 2 (P< 0.0001, 95%CI 191–547). Mean inpatient stay was 8.0 days in group 1, and 4.8 days in group 2 (P< 0.0001, 95%CI 3.4–6.0).

Minimum follow-up was 3 years in group 1 and 1.5 years in group 2. There were 3 dislocations in group 1, and none in group 2. There were 2 re-operations in both groups. The relative improvement in WOMAC scores was significantly greater in group 2 at 3 months and 1 year (P< 0.05).

Conclusion The PSMI approach to the hip is truly soft-tissue sparing. It is safe and relatively easy to perform. The stability and minimal morbidity allow early mobilisation. This is the first study to suggest the benefits of minimally invasive surgery may be prolonged. Cosmesis is a by-product rather than primary objective.

Introduction and Aims: A number of ‘minimally invasive’ approaches have been described which are essentially a standard approach through a smaller incision: the term ‘mini-incision’ is more appropriate. We describe a new technique that is truly soft-tissue sparing and report our early results.

Method: Following Malchau’s principles we performed cadaver studies to familiarise ourselves with the approach before conducting a pilot study. The approach involves a 6–8cm oblique incision over the posterior aspect of the greater trochanter. Care is taken to preserve piriformis and gluteus maximus. Meticulous capsular repair is performed through drill holes into bone at the end of the procedure to reconstruct the posterior envelope. There are no restrictions to mobility post-op.

Patients were scored pre-operatively and followed up prospectively. The only special instruments required are two large curved Hohmann retractors and an angled cup introducer.

Results: One hundred and one consecutive routine primary total hip replacements were performed via the ‘piriformis-sparing minimally invasive approach’ by a single surgeon. Marked on-table stability was noted in all hips prior to capsular repair.

Forty-two percent of patients were male. Mean age was 68.9 years (42–90) and BMI 26 (14–39). Average operation time was 64.1 minutes and anaesthetic time 92.5 minutes. Mean fall in haemoglobin in the first 24 hours was 2.3g/dl. Mean incision length was 7.4cm.

Follow-up was a minimum of one year (range 12–29 months). There was a highly statistically significant improvement in WOMAC and SF-36 scores at three and 12 months post-operatively (p< 0.0001). Early medical complications occurred in 12 patients, including two superficial infections, all of which resolved. There were no peri-prosthetic fractures and importantly, no dislocations. There were two re-operations: one revision for cup displacement and one washout for deep infection.

Conclusion: We believe that the marked stability that we achieve on-table is only possible by sparing piriformis and careful capsular repair. As with all new procedures however, there is a learning curve for both surgeon and assistant. Preliminary results from our pilot study may be interpreted with guarded optimism.

Introduction and Aims: Iontophoresis is a method to introduce antibiotic molecules into allograft bone using an electrical potential. In-vitro testing has shown that these antibiotics should be released in their bioactive form at therapeutic levels for extended periods of time. This is the first report of iontophoresed allograft implantation into patients.

Method: A method of loading tubular sections of cortical bone was used in theatre prior to implantation. The bone was held vertically in an antibiotic bath with a cylindrical outer electrode and a wire electrode down the centre of the bone. An electrical potential of approximately 90V was applied to drive the antibiotics into the bone. Post-operative serum, drain and allograft antibiotic assays were performed. All patients were followed-up clinically and radiologically. Patients who required a bulk segmental allograft from June 1997 to present were entered into the trial and received iontophoresed bone.

Results: Since June 1997, 35 patients have received 37 iontophoresed allografts. Indications for allograft insertion were limb salvage for tumor (16), poor bone stock associated with infection (12), periprosthetic fracture (seven), aseptic loosening (one) and recurrent dislocation of total hip replacement (one). One patient had acute complications requiring amputation. No patients were lost to follow-up with a mean follow-up of 3.3 years. Two patients required an allograft exchange for fracture and infection. There were two late allograft infections at 10 and 18 months. One patient was revised to another iontophoresed allograft and has had no recurrence at two years. The other infection required above knee amputation. One allograft was revised with allograft exchange and vascularised fibular graft following fracture of metal fixation. There was one case of persistent non-union in a knee fusion, which was treated after 21 months by removal of the intermedullary fixation and allograft and use of an Ilizarov frame. All other allografts are in-situ with no complications related to the allograft. Twelve patients had pre-existing proven infections. None of these patients have been re-infected to date. Therapeutic gentamicin and flucloxacillin levels were detected in drain fluid samples post-operatively, averaging from 39.9 mg/L at two hours to 5.97mg/L at 48 hours for gentamicin and 16.83mg/L at two hours and 2.23 mg/L at 48 hours for flucloxacillin. This was significantly greater than the minimum inhibitory concentration (MIC) against Staphylococcus aureus for gentamicin (0.25mg/L) and flucloxacillin (0.30mg/L). At the same time, blood levels remained in a safe range.

Conclusion: Iontophoresis is a safe and inexpensive method that can be executed in the operating theatre. Iontophoresed bone delivers a high local dose of antibiotic, which may prevent early biofilm formation initiated during allograft handling and exposure to theatre air. With no early infections and no re-infections, further assessment of this technique continues with guarded optimism.