The primary objective of this study was to evaluate the performance of the Acrobot^® Sculptor system in achieving a surgical plan for implantation of unicompartmental knee prostheses, compared with conventional surgery. The Acrobot^® Sculptor is a novel hands-on medical device, consisting of a high speed cutter mounted on a robotic device which the surgeon holds and directs.

A prospective, randomised, double-blind (patient and evaluator), controlled versus conventional surgery study was undertaken and has been fully reported in Journal of Bone and Joint Surgery (British), 88-B.

All (13 out of 13) of the Acrobot^® cases were implanted with tibio-femoral alignment in the coronal plane within ±2° of the planned position, while only 40% (six out of 15) of the conventionally performed cases achieved this level of accuracy.

There was also a significant enhancement in the extent of post-operative improvement, as measured by American Knee Society (AKS) Scores at six weeks, in the cases implanted with the Acrobot^®. The difference between type of surgery is statistically significant (p=0.004, Mann-Whitney U test). Operating time (skin to skin) is higher in Acrobot treated subjects, but the difference between the two types of surgery fails to reach significance.

The Acrobot^® System was found to significantly improve both accuracy and short term outcome in this investigation. By permitting the creation of bone surfaces that can be machined by means other than an oscillating saw, the Acrobot^® System paves the way for novel implant designs to be developed, facilitating bone conserving arthroplasty in the knee, hip and spine with a new generation of even less invasive but more reliable procedures.

Introduction: Malignant tumours of the fibula are rare and can be difficult to treat. We discuss the management and outcome of 52 patients who presented with malignant tumours of the fibula over a 15-year period between 1983 and 1998.

Methods: Data was collected prospectively and reviewed from the Bone Tumour database, medical records and by clinical review. Consecutive patients were studied and survival was calculated using the Kaplan-Meier curve.

Patients: The tumour type was Osteosarcoma (23 patients), Ewing’s sarcoma (16), Chondrosarcoma (11 – of which 10 low grade) and Malignant Fibrous Histiocytoma (2). We concentrate on the two most common frankly malignant groups: Osteosarcoma and Ewing’s. The male:female ratio of patients with Osteosarcoma was 11:12 and with Ewing’s Sarcoma was 11:5. Mean age for Osteosarcoma was 21.5 years and for Ewing’s Sarcoma was 14.2. The most common site of tumour was in the proximal fibula in both Osteosarcoma (19 / 23) and Ewing’s Sarcoma (10 / 16). The stage of disease at presentation was IIa or IIb in the majority of patients, with seven patients presenting with metastases.

Management: The current investigative procedures are Radiographs, Magnetic Resonance Imaging, Radioisotope Bone Scans, Computerised Tomography of the chest and needle biopsy whereas in the past CT of the lesion and open biopsy were common. Chemotherapy was administered as per protocol at the time of diagnosis and radiotherapy was given in selected cases. Surgery was performed on all but 3 patients, who were unfit and died. This consisted of local en bloc resection in 86.3% and above knee amputation in 6.8%.

Outcome: Whereas all the diaphyseal and distal lesions were completely excised, 9 out of 26 proximal lesions had a marginal excision, 4 of which had open biopsies. The common peroneal nerve was sacrificed in 50% of cases and this had no link to survival. The overall 5-year survival was 33% for Osteosarcoma and 40% for Ewing’s Sarcoma, with proximal lesions doing much worse than diaphyseal and distal lesions. Patients who had marginal excisions all died within 2.5 years.

We performed a prospective, randomised controlled trial of unicompartmental knee arthroplasty comparing the performance of the Acrobot system with conventional surgery. A total of 27 patients (28 knees) awaiting unicompartmental knee arthroplasty were randomly allocated to have the operation performed conventionally or with the assistance of the Acrobot. The primary outcome measurement was the angle of tibiofemoral alignment in the coronal plane, measured by CT. Other secondary parameters were evaluated and are reported.

All of the Acrobot group had tibiofemoral alignment in the coronal plane within 2° of the planned position, while only 40% of the conventional group achieved this level of accuracy. While the operations took longer, no adverse effects were noted, and there was a trend towards improvement in performance with increasing accuracy based on the Western Ontario and McMaster Universities Osteoarthritis Index and American Knee Society scores at six weeks and three months. The Acrobot device allows the surgeon to reproduce a pre-operative plan more reliably than is possible using conventional techniques which may have clinical advantages.

Introduction and Aim: This project reports on patients treated with malignant fibula pathology at the London Bone Tumor Service with the aim of reporting on the prognosis for such patients.

Method and Results: Over a 15-year period, The London Bone Tumor Service has treated 39 patients with malignant fibula pathology: Osteosarcoma (23), Ewing’s sarcoma (16). Proximal fibula pathology was more common (29), distal (five) and diaphyseal (five). Thirty-two patients were treated with wide local excision initially, one below knee amputation, three above knee amputations, two were not fit for surgery and two died while receiving chemotherapy. Two patients required subsequent above knee amputations and one patient a hip disarticulation. Relapse was very common in proximal fibula osteosarcoma. Only 7/23 patients avoided both metastasis and local recurrence.

The five-year survival rate of osteosarcoma of the proximal fibula is 33%, distal fibula 100% and diaphyseal 100%. Ewing’s sarcoma of the proximal fibula is 40%, diaphyseal 50% and distal fibula 100%.

Conclusion: Despite relatively early presentation of symptoms, the prognosis of proximal fibula osteosarcoma and Ewing’s remains poor. Unlike the prognosis of both distal and diaphyseal pathology, which remains excellent.

We report the use of CT with 3D reconstruction to determine the accuracy of knee arthroplasty.

Method Pre- and post-operative CT scans have been performed in a cohort of 20 total and unicompartmental knee replacements in fine detail of hips, knees and ankles but with minimal dosage elsewhere.

Three different methods have been used to measure the position of the implant.

‘True’ anterior posterior views are reconstructed from the post-operative CT data and tibiofemoral angles computed.

Results Alignment can be determined within 0.5° using method 1. With the addition of method, 2 rotational malalignment can be computed. With method 3 a transformation matrix is provided, showing the position in space of the prosthesis relative to the pre-op plan, with accuracy of under 0.5 mm. Poor function is explained.

Conclusion We have used 3-D reconstructions from CT scans and digital measurements to compute the precise position of the implant in the bone. Showing where the implant lies in 3D space explains accurately why poor results have occurred. CT based planning has been used to ensure that the bone cuts are planned correctly. Postoperative CT scans confirm that if the plan is achieved, function will be good.

The accuracy of prosthesis implantation is closely related to their function and longevity; we report the development of an active constraint robot for minimally invasive unicompartmental knee arthroplasty (UKA) using CT and knee scoring.

Method: Pre and postoperative CT scans are performed. Pre-op scan CT scans were used to plan the precise position of implants on the bones. The femoral and tibial bone cuts were then generated, together with the software boundaries that constrain the surgeon. This plan was then used to define the cutting planes of the ‘Acrobot’ active constraint device that we have developed.

The Postoperative CT scan was compared with the preoperative plan. The distance of the joint line from the hip and ankle joint, and its angulation and rotation were compared to the preoperative plan. In addition, the position of the implants relative to their planned position has been computed.

Results: No significant complications have been encountered. Using the postoperative CT scans, in no case is the implant more than 2mm or 2 degrees from the planned position.

Conclusions: The Acrobot system for UKA has completed its preliminary trial satisfactorily. It provides a hands-on operation but with robotic levels of accuracy, through a minimally invasive approach. By abolishing outliers, it improves outcomes in UKA replacement.

Introduction: Active Robots have been shown to be effective at performing arthroplasty, but some hesitation has been felt by the surgical world. The lack of human interface in the procedure has been one of the stumbling blocks towards wider acceptance. The Acrobot has been developed, at Imperial College London, in collaboration with University College London to allow the surgeon to perform the surgery himself, but with active constraint, preventing him from taking too much bone, or straying into soft tissue.

Materials and methods: A preoperative planning system is used, based on ct data acquired without fiducial markers. Semi-automated segmentation is performed. The surgeon then performs the virtual surgery on the bones on screen, allowing precise sizing, and orientation. The safe field of activity is then defined, within which the surgeon is free. The patient is positioned on the operating table and immobilised. Anatomic registration is then performed, and when sufficient accuracy obtained, the milling procedure is begun. A high speed electric milling tool is used, and with it the bone planes are prepared sequentially. The prosthesis is then inserted in standard fashion.

Results: Laboratory testing on dry bone and cadaveric models have confirmed that the registration process is now accurate. At the moment we are using a classical ICP algorithm to register the data points. For this test the Root Mean Square is 0.626 mm in a cadaveric model. This pinless anatomic registration can be achieved rapidly, if the initial siting points are accurately identified.

Conclusion: The active constraint concept seems to be a safe and user friendly way of achieving robotic level accuracy with a human touch. Anatomic registration using the robot is accurate, and early clincal trials of total knee arthroplasty are encouraging.

Massive cemented endoprosthesis are used to enable early resumption of activity after tumour surgery. The longevity of the prosthesis varies with anatomical site, pros-thesis type, and mode of þxation. Revision surgery will be required in approximately 50% of cases of endopros-thetic replacements around the knee by 10 years because of aseptic loosening. Insertion of a second cemented endoprosthesis is a challenge because of the poor quality of the remaining bone and loosening recurs quickly. The use of extracortical plate þxation in joint sparing surgery where the remaining bone after tumour resection will not accept an intramedullary stem is also described.

The þrst series of 14 patients with extracortical plate þxation in difþcult revision or joint-sparing tumour surgery with a mean follow-up of 5 years are described. The three-plate design incorporates well within a remodelled cortex to achieve osseomechanical integration with all patients regaining their premorbid level of function within 5 months. At 5 years the Enneking scores averaged 27.3.

One revision was required in a femoral replacement because of loosening. It was possible to insert a new endo-prosthesis as the intramedullary bone had reconstituted.

The preliminary results suggest that this technique may provide an easy, biomechanically friendly alternative to a device with an intramedullary stem, which has a shorter lifespan in revision tumour surgery.

The Acrobot®, an active constraint “hands-on” robotic system, gives navigation cues to the surgeon, and also assists him in the surgery, using active software constraints if he tries to depart from the preoperative plan. It has just entered clinical trials. We report the first 5 cases.

The Acrobot® system for precision total knee arthroplasty comprises the following components:

1. A CT-based planning system

a gross positioning device with separate brakes and encoders, locked off for safety during the procedure,

4. The Acrobot’s software which:

imports the preoperative plan,

Each patient’s knee scores were monitored and postoperative CT scan was compared with the preoperative plan.

Seven robot assisted arthroplasties have been performed. No significant complications have been encountered. The Knee and Womac Scores show that the procedure is safe and comparable to conventional surgery in the early postoperative period. The envelope of error on postoperative CT scans has been within the accuracy of the method of measurement, at < 1 mm and < 10 without the outliers which haunt every clinical series.

The Acrobot® system for total knee arthroplasty has completed its preliminary trial satisfactorily. It provides a handson operation but with robotic levels of accuracy. It is suitable for conventional open surgery, but its real place will be in the arena of minimally invasive unicondylar knee arthroplasty, hip arthroplasty and resurfacing, and in the spine, where active constraint will prevent potentially dangerous surgical errors.

We have investigated nine patients with cemented Furlong (JRI, London, UK) titanium hip replacements who presented with early pain despite a well-fixed, aseptic prosthesis. All were followed up clinically and radiologically at regular intervals. Pain was located in the thigh and was worse at night. Radiographs showed cortical hypertrophy of the femur around the tip of the stem. Eight of the nine patients subsequently required single-stage revision using an uncemented prosthesis, which relieved the pain. At revision, the pH of the tip of the stem was found to be highly acidic with macroscopic evidence of corrosion consisting of multiple layers of titanium oxides when studied by X-ray dispersive analysis. Cemented titanium implants have a potential for crevice corrosion leading to cortical hypertrophy and intractable pain.

We discuss the management and outcome of 52 patients who presented with malignant tumours of the fibula over a 15-year period between1983 and 1998.

The tumour type was Osteosarcoma (23 patients), Ewing’s sarcoma (16), Chondrosarcoma (11 – of which 10 low grade) and Malignant Fibrous Histiocytoma (2). We concentrate on the two most common frankly malignant groups: Osteosarcoma and Ewing’s.

The male:female ratio of patients with Osteosarcoma was 11:12 and with Ewing’s Sarcoma was 11:5. Mean age for Osteosarcoma was 21. 5 years and for Ewing’s Sarcoma was 14. 2. The most common site of tumour was in the proximal fibula in both Osteosarcoma (19 / 23) and Ewing’s Sarcoma (10 / 16). The stage of disease at presentation was IIa or IIb in the majority of patients, with seven patients presenting with metastases.

The current investigative procedures are Radiographs, Magnetic Resonance Imaging, Radioisotope Bone Scans, Computerised Tomography of the chest and needle biopsy whereas in the past CT of the lesion and open biopsy were common. Chemotherapy was administered as per protocol at the time of diagnosis and radiotherapy was given in selected cases.

Surgery was performed on all but 3 patients, who were unfit and died. This consisted of local en bloc resection in 86. 3% and above knee amputation in 6. 8%. Whereas all the diaphyseal and distal lesions were completely excised, 9 out of 26 proximal lesions had a marginal excision, 4 of which had open biopsies. The common peroneal nerve was sacrificed in 50% of cases and this had no link to survival.

The overall 5-year survival was 33% for Osteosarcoma and 40% for Ewing’s Sarcoma, with proximal lesions doing much worse than diaphyseal and distal lesions. Patients who had marginal excisions all died within 2. 5 years.

To assess the clinical features, development of metastases, and survival rate of patients with local recurrence after the resection of osteosarcoma in a large series.

Five hundred and thirty (530) patients with high-grade osteosarcoma were treated between 1989 and 1998. Fifty-four patients (10%) developed local recurrence after resection and adjuvant chemotherapy. There were 38 men and 16 women with a mean age of 19 years (range 6–50). The mean follow up was 39 months (range 7–120 months). Forty-three patients (79%) had clear resection margins microscopically, while in 8 patients (15%) microscopic tumour was found at the resection margin, and contaminated excision was performed in 3 patients. Histological response was category 1 in 24% of the patients, and category 2 in 76%. Clinical features, treatment, and prognosis were analyzed. Survival rates were examined using Kaplan-Meier Analysis.

The average interval between the first resection and local recurrence was 15 months (range 2–109 months). Forty-one patients (76%) had local recurrence in deep soft tissue, 7 in bone, and 6 in subcutaneous tissue. Twenty-six patients (49%) had lung metastasis at the time of local recurrence, while 21 patients (38%) developed it later. Thirty patients (57%) were treated with resection of the recurrent lesion and 18 (32%) were treated with amputation. 1-, 3-, and 5-year survival rates after local recurrence were 0.57, 0.38, and 0.22 respectively.

87% of patients with local recurrence developed metastases either concurrently or at a later date. Immediate amputation did achieve local tumor control. However, the survival rate was not statistically higher.

Needle biopsies, performed on 208 consecutive patients and interpreted at the London Bone Tumour Service over a two-year period, were reviewed. A correct diagnosis was reached in 97% (133 out of 137) using this technique alone. Needle biopsy is safe and accurate when undertaken in consultation within a bone tumour service; it offers considerable advantages to both patient and surgeon over conventional open biopsy.

There is no firm published evidence to support the use of closed suction drains. Over 20 years ago, large studies by the Public Health Laboratory Service and the National Research Council found that drains were risk factors for wound infection. A prospective randomised study of the use of closed suction drains after surgery for fractured neck of femur in 70 patients failed to show that drains improved wound healing. Drained cases had more complications.