Aim

Culture-based conventional methods are still the gold standard to identify microorganisms in hip and knee PJIs diagnosis. However, such approach presents some limitations due to prior antimicrobial treatment or the presence of unusual and fastidious organisms. Molecular techniques, in particular specific real-time and broad-range polymerase chain reaction (PCR), are available for diagnostic use in a suspected PJI. However, limited data is available on their sensitivity and specificity.

This study aimed to evaluate the performance of a rapid and simple Investigational Use Only (IUO) version of the BioFire® JI multiplex PCR panel when compared to traditional microbiological procedures.

Aim

Analysis of microbiological spectrum and resistance patterns as well as the clinical outcome of patients who underwent a Debridement, antibiotics and implant retention (DAIR) procedure in the early phase following failed two-stage exchange arthroplasty of the knee and hip.

Purpose

Unexpected-positive-intraoperative-cultures (UPIC) in presumed aseptic revision-total-knee-arthroplasties (rTKA) are common, and the clinical significance is not entirely clear. In contrast, in some presumably septic rTKA, an identification of an underlying pathogen was not possible, so called unexpected-negative-intraoperative-cultures (UNIC). The purpose of this study was to evaluate alpha defensin (AD) levels in these patient populations.

Aim

Dalbavancin is a novel second-generation lipoglycopeptide antibiotic with strong activity against many gram-positive bacteria and a prolonged half-life of 6–11 days. This allows a once-a-week intravenous application and therefore an outpatient intravenous therapy. Currently, only little is known about the use of Dalbavancin in Periprosthetic joint infection (PJI). The aim of this retrospective study, was to compare the outcome of hip and knee periprosthetic joint infections (PJI) in patients who received dalbavancin (DAL) with patients which was treated by standard of care antimicrobial agents (SoC).

Aim

Little is known about microbiological spectrum and resistance patterns as well as the clinical outcome in patients who undergo a repeat first stage procedure as part of a 2-stage revision arthroplasty for the treatment of periprosthetic hip and knee joint infections.

Aims

Pelvic reconstruction after the resection of a tumour around the acetabulum is a challenging procedure due to the complex anatomy and biomechanics. Several pelvic endoprostheses have been introduced, but the rates of complication remain high. Our aim was to review the use of a stemmed acetabular pedestal cup in the management of these patients.

Aim

Until now, there has been no consensus as to whether stemmed acetabular components are appropriate for use in patients undergoing revision total hip arthroplasty (THA) who have major acetabular defects or pelvic discontinuity. We wished to address this deficiency in the literature.

INTRODUCTION

Total knee replacement is mostly done with alignment rods in order to achieve a proper Varus / Valgus alignement. Other techniques are computer assisted navigation or MRI based preoperative planning. iASSIST™ is a computer assisted stereotaxic surgical instrument system to assist the surgeon in the positioning of the orthopaedic implant system components intra-operatively.

It is imageless and the communication between the PC and the “Pod's” does not require any direct camera view, it is a bluethooth comunication system. This study presents preliminary results utilizing iASSIST™.

The aim of this study was to test and compare radiographic alignment, functional outcomes, and perioperative morbidity of the iASSIST™ Knee system versus conventional total knee arthroplasty.

Introduction

In revision surgery, detection of periprosthetic joint infection is of prime importance. Valuable preoperative and intraoperative diagnostic tests and tools are necessary. The classical standard procedures are puncture and bacteriology examination, frozen section intraoperative and powerfield micro analysis.

Since autumn 2014 a new device for detection of periprosthetic joint infection is available, named Synovasure. It is a fast test for the detection of Alpha defensing, which plays a major role in the antimicrobial defence and only occurs in inflammatory processes.

„The alpha-defensin test is an immunoassay that measures the concentration of the alpha-defensin peptide in human synovialfluid. A-Defensin is an antimicrobial peptide that is secreted into the synovial fluid by human cells in response to pathogenic presence” (Deirmengian C et al., CORR 2014).

Summarized, the evidence of Alpha defensin indicates infection. It is produced by CD Diagnostics (Wynnewood, PA, USA) and merchandised by Zimmer (Warsaw, IL, USA).

We are using Synovasure in daily routine at our department since September 2014. The aim of this conducted study is to present our first clinical experience and to report our results of the first 54 cases.

BACKGROUND

Despite many years of clinical experience the optimal bearing choice in total hip arthroplasty (THA) remains controversial. This study aims to directly compare the three widely used bearing surfaces: metal-on-highly crosslinked polyethylene (MoHXLPE), ceramic-on-ceramic (CoC) and metal-on-metal (MoM), regarding clinical and radiologic outcome parameters.

Introduction

The legacy constrained condylar knee prosthesis (LCCK, Zimmer.) is designed for primary and revision total joint arthroplasties that need additional stability due to ligament deficiency and to compensate for bone defects. In this follow-up we present our mid term results.

Background

Modular endoprostheses today represent a standard treatment option in the management of musculoskeletal tumors of the lower extremities. Long-term results of these reconstructions, however, are often limited by the course of the underlying disease. We therefore report our experiences in cancer patients with megaprostheses of the lower limb after a minimum of 15 years.

Aim

Preoperative serum CRP has been identified as an independent predictor in various malignancies. For osteosarcoma, however, the value of serological markers is unreliable. Aim of this study was to evaluate the prognostic power of preoperative CRP in patients with osteosarcoma.

Endoprosthetic replacement following oncological conditions has shown to be at higher risk of sceptical complications due to the use of implants of unusual size, major soft tissue loss and immunsupression.

373 patients have been treated at our institution for malignant tumours of the bone or soft tissue around the knee with a modular tumour-prostheses of the knee joint since their availability from 1978. Infection or septic complications were identified in 78 patients (20.9%).

In 15 cases of superficial wound healing disturbances with a fistula simple excision and revision of the wound was performed. In 48 cases of deep periprosthetic infections patients underwent one-stage revision with explantation of the total prosthetic material except femoral and tibial stems, extensive debridement of the wound and replantation of the disinfected prostheses throughout one operation. In 8 patients two-stage revision of the prostheses was performed, using an antibiotic impregnated cement spacer and Steinmann nails. In 5 patients amputation of the affected limb was indicated, whereas 2 patients could be treated conservatively. Out of the patients treated by one-stage revision 16 developed recurrent infection and had to undergo consecutive surgery. After two-stage surgery 4 patients showed signs of septic recurrence.

According to our results deep periprosthetic infection of tumour-prostheses primarily can be treated by one-stage revision, in recurrent infections, however, two-stage revision should be performed. We additionally suggest the use of local or pedicled muscle flaps to obtain better soft tissue coverage of the prostheses after infection.

Resection of the upper limb together with the shoulder girdle is known as forequarter amputation. In selected patients, this type of resection may have to be extended to a resection including parts of the thoracic wall in order to achieve local tumour control in advanced stages of neoplasms. Although, forequarter amputation alone is well described, reports on its combination with parts of the chest wall only consist of few case reports, while larger experiences and systematic reviews of its obstacles and complications are missing.

A series of six patients, five females and one male with, average age 58 years (range 41 to74 years), undergoing forequarter amputation with partial chest wall resection has been treated for malignancies around the shoulder at the Medical University of Vienna since 1993, thereby, to our best knowledge, presenting the largest series published to date. Patient data of all departments involved were retrospectively analysed and patients were followed-up according to standard oncological protocols. The underlying disease was malignant schwannoma in two, undifferentiated sarcoma in two, osteosarcoma in one and squamous cell sarcoma in one. A vast tumour of the shoulder and axillar space, uncontrollable pain, lymphedema, partial loss of function of the affected limb and ulceration indicated treatment.

All patients underwent radical amputation of the upper limb and all structures of the shoulder girdle including two to seven ribs. Chest wall reconstruction was achieved by a PTFE patch alone or in combination with a Stratos^®-implant. Myo-cutaneous reconstruction was performed by a pedicled (n=3) or a free myo-cutaneous forearm flap (n=3). There were no cases of peri-operative mortality. In two patients full forearm flap necrosis occurred and indicated two revisions in each with coverage by a free flap. One patient suffered vascular complications and underwent five revisions. Average follow-up was 14 months (range 5 to 35 months). Median survival was 8.5 months, with three patients still alive at the time of this investigation. Three patients died of systematic metastatic disease between 5 and 35 months after surgery. Two patients were successfully supplied with myo-electrical prostheses.

The key issues for surgical management of the resulting defect were

the restoration of mechanical chest wall stability,

Although forequarter amputation is a mutilating operation and in advanced stages of disease certainly can only temporarily limit disease progression, in selected cases, it may remain an option in vast tumours of the shoulder girdle.

Background: Endoprosthetic reconstruction has become the gold standard of treatment after the resection of tumors around the proximal femur, however, the rate of complications linked to megaprostheses is clearly higher than with standard implants. Aim of this study was to investigate the incidence and type of complications related to modular proximal femur prostheses.

Patients and Methods: By retrospective database analysis of the Vienna Tumor Registry, we evaluated the incidence of complications in 170 consecutive patients who have received a proximal femur KMFTR/GMRS at our institution between 1982 and 2007. 71 patients with an average age of 41.7 years (range 18.2–79.9 years) received the implant following the resection of a malignant bone tumor, 95 patients with an average age of 61.7 years (range 5.9–84.2 years) due to metastatic disease. The average time of follow-up was 3.5 years (SD ±4.9 years).

Results: Overall patient survival at five years was 32%. For patients with metastatic disease the overall survival was 10% at five years. Patients being treated for a primary bone tumor had an overall survival of 55% at 5 years. The overall survival of the prosthesis was 90% at two years and 72% at five years. Twenty-one patients (12.65%) suffered from dislocation after a mean time of 6.5 month (range 0.3–33 months) after surgery. Out of these, nine had to be treated by open reduction. Nine patients suffered recurrent dislocation after their first event. Patients who underwent extensive pelvic reconstruction had a significantly higher dislocation rate (33.3%) compared to patients with no or standard acetabular components (11.2%). Deep infection occurred in twelve patients (7.3%) after a mean of 39 months (range 1–166 months) after surgery. Treatment of infection was one-stage revision in eight and hip disarticulation in one patient. Two patients were successfully treated by local wound revision. One patient died of septic shock four days after surgery. Re-infection occurred in three patients. Aseptic loosing occurred in 13 patients (12.8%) after a mean time of 75.6 months (range 1–223 months) after surgery. Revision surgery was necessary in 27 patients (15.8%) with a mean time to first revision of 32 months (range 0.3–116 months). Prosthetic fracture was found in two patients. Local recurrence occurred in 14 patients (8.4%). In seven patients (4.2%) amputation was necessary.

Conclusion: Modular endoprosthesis allow excellent reconstruction of the proximal femur following tumor resection. However, the main complications, dislocation and infection, still remain considerable drawbacks.

In order to understand the role and efficacy of vascularized fibular graft and massive allograft in reconstruction of the knee, we have analyzed and review 25 patients of primary malignant bone tumours within 5 cm around the knee, that were managed primarily by this technique. In 4 patients the distal femur was affected while the proximal tibia was affected in 21 patients. There were 16 male and 9 female with an average age at the time of surgery of 19.7 years (range; 5 to 52), 17 patients (68%) were skeletally immature. The pathology was mostly represented by Osteosarcoma and Ewing sarcoma (15) and 18 patients (72%) received pre-operative chemotherapy. The resection of the tumor was transepiphyseal in 13 patients (52%) and intercalary in 12 patients (48%). The method of reconstruction was mainly concentric (allograft and fibula inside in 22 patients, 88%), while fixation was done principally by diaphyseal plate and metaphyseal screws (14 patients, 56%). Only three flaps failed (12%) detected by postoperative bone scan and confirmed by the clinical follow up. Twelve patients (48%) had 17 local complications (68%). Management of these complications succeeded to control them in nine patients (75%). The average time of union of fibula was 5.6 month (range: 3–10). The average time of union of allograft was 19.6 month (range: 10–34). All allograft united primarily (92%) except two cases; one case required bone graft and re-platting at 13 month postoperative after implant failure to achieve union 2 months later ; the other had infected non-union of allograft and amputation was done. Functional results were evaluated using the modified 30-points Musculoskeletal Tumor Society rating score (MTSRS) at final follow up of average 143 month (range; 28–213): the average total score was 27.4 (range; 18 to 30). All patients had good functional range of motion of the knee with stable knee at final follow up and were able to perform sport. Long term results of this study clearly indicates that allograft and vascularized fibular graft is a useful limb salvage procedure providing a biological long-term solution especially in skeletally immature. This technique provides single stage life long reconstruction. The allograft shell provide early stability and fixation to support a small epiphyseal fragment to preserve the articular surface and the vascularized fibula provides revascularization and osteointgration with the allograft to finally offer a long lasting durable reconstruction with full rang of motion of the knee.

Besides the femur and the tibia, the humerus is the third most common localisation of osteosarcoma. 78 patients with osteosarcoma of the humerus have been treated at our institution since 1934. Among these, 7 patients have been admitted before implementation of the Vienna Tumour Registry in 1968, additionally 4 patients had undergone primary surgical resection at another institution. This left 67 patients for follow-up after multi-modal therapy of humeral osteosarcoma comprising neo-adjuvant and adjuvant chemotherapy and surgical resection. (38 males and 29 females with an average age of 21.8 years, range 3.6 to 73.2 years) The subtypes of tumours observed were classic osteosarcoma in 56 patients, parostal sarcoma in 4, teleangiectatic sarcoma in 3, secondary sarcoma in 2 (one in Morbus Paget and one after radiation of a hemangioendothelioma), high-grade surface sarcoma in 1 and a humeral lesion within a multifocal osteosarcoma in 1. The localisation was foremost the proximal humerus (61) and rarely affecting the distal (5) or total bone (1). 11 patients suffered from pulmonary metastases upon primary diagnosis. In 9 cases resection alone was indicated. 9 patients underwent a resection-replantation-plasty, and in 2 patients primary amputation was performed. 46 patients were treated by resection and endoprosthetic reconstruction using ceramic prostheses (7), custom-made endoprostheses (13) or humeral HMRS modular prostheses (26). Before 1980 a non-standardised neo-adjuvant and adjuvant chemotherapy was administered in 12 patients, all patients thereafter received a chemotherapeutic regimen according to the COSS or EURAMOS-1 protocol. In 3 patients with parostal sarcoma no adjuvant therapy was indicated. The patient with multifocal osteosarcoma was treated conservatively by chemotherapy, radiation and immunotherapy by dendritic cell vaccination. The overall survival was 58% at 5 years. 23 patients died of their disease at an average of 25 months after operation (range 2 to 135 months). Average follow-up of the remaining patients was 91 months. (range 1 to 389 months). 4 patients treated before 1982 developed local tumour recurrence leading to secondary amputation in all cases, and death of disease within 12 months in 3 cases, respectively. 16 patients had to undergo one or more revisions, including secondary amputation in 2. Pulmonary metastases were observed in 15 patients, 2 patients developed skeletal metastates. After resection of metastatses, 14 patients died of disease, among them 9 patients died within 12 months after operation. Upon latest follow-up, 3 patients were alive disease-free, the patient with multifocal osteosarcoma was alive with disease 22 months after primary diagnosis. The multimodal treatment of osteosarcoma shows satisfactory oncological results. The implementation of standardised chemotherapeutic protocols has improved overall outcome.

The treatment of deep prosthetic infection in cancer patients with tumour prostheses remains the major complication to be dealt with in this population.

The Vienna Bone Tumour Registry includes information of more than 6500 patients of a period of 36 years. 145 patients with malignant proximal femoral tumors had resection and limb salvage with an uncemented Kotz modular femoral and tibial reconstruction megaprosthesis (KMFTR). There were twenty osteosarcomas, thirteen Ewing’s sarcomas, six chondrosarcomas, six plasmozytomas, three fibrosarcomas, three liposacomas and others. Thirteen patients (7 males, 6 females with an average age of 45 years, range 10 to 75 years) suffered from deep prosthetic infection within an average of 44 months after primary implantation, representing an infection rate of 8,97 percent.

Average follow-up was 109 months, range 7 to 339 months. Two patients with only mild signs of infection were treated by a conservative antibiotic regimen. Nine patients were treated by one-stage revision. One of the remaining two patients with severe infection underwent exarticulation of the hip as primary intervention, the other patient died due to general sepsis on the fourth post-operative day. Six patients showed no further signs of infection. Six patients, however, required one or more reoperations due to recurrent prosthetic infection. Among these four patients have successfully been treated by repeated one-stage revision, in two patients the prosthesis had to be removed permanently.

Deep prosthetic infection around modular tumour prostheses of the proximal femur and hip seems to be less common compared to distal femur, knee or tibia. However, the treatment of this complication has a higher failure rate due to multiply recurrent infection.

Hyperactivation of the epidermal growth factor receptor (EGFR) by gene amplification, mutation as well as overexpression is a hallmark of multiple human carcinomas. However, in recent years data have accumulated that EGFR-mediated signals might also contribute to malignant progression and therapy resistance of human sarcomas. Consequently we have investigated if human osteosarcoma cell lines (n=9) express functional EGFR and its useability as therapeutic target. Osteosarcoma cells expressed distinctly differing level of EGFR reaching in some cases high amounts. However, even low expression levels were sufficient to activate both MAPK and PI3K pathways (determined by phosphorylation of ERK1/2 and S6, respectively) following EGF exposure of serum-starved cells. The EGFR-specific inhibitor gefitinib completely blocked EGF-mediated and attenuated serum-induced downstream signal activation. While gefitinib applied as single agent demonstrated only limited growth inhibiting activity in short term experiments (72h drug exposure), it led to reduced colony formation in long term experiments in the majority of cell lines. Importantly, gefitinb sensitized EGFR-expressing osteosarcoma cell lines against chemotherapy with doxorubicin and methotrexate, while it antagonised cisplatin-induced cell death. Summarizing, our data suggest that EGFR-mediated survival signals protect human osteosarcoma cells against the cytotoxic activity of several antineoplastic drugs. Consequently, combination approaches including EGFR inhibitors in addition to chemotherapy should be evaluated for treatment of high grade osteosarcoma patients.

Introduction: Little data are available about the incidence and the management of hip dislocation following the implantation of megaprosthesis of the proximal femur, which is one of the main complications following this procedure.

Material and Methods: 190 patients, who received a proximal femur KMFTR/GMRS at our institution between 1982 and 2007, were retrospectively reviewed with regard to the incidence of hip dislocation as well as the success rate of the subsequent surgical/non-surgical treatment. A proximal femur tumor endoprosthesis was used in 148 patients following the resection of a malignant tumor and in 43 patients in severe revision cases following total hip arthroplasty. The average age at the time of surgery was 48 [6a to 83a] in the tumor group and 57.3 [45a to 78a] in the revision group. All of the revision cases and 12 patients from the tumor group had additional revision cups, such as the Schoellner pedestal cup.

Results: 12.3 % (18/147) of the tumor patients and 13.9% (6/43) of the revision cases dislocated at least once. 66.7% (12/18) of the first dislocations from the tumor and 50 % (3/6) of the revision group were treated with closed reduction, the rest required surgery. All patients received an abduction cast for at least 8 weeks. 38% (7/18) of the dislocated hips of tumor group (4.8% [7/147] total) and 67% (4/6) of the revision group (9.3% [4/43] total) experienced a second dislocation. 57% (4/7) of the dislocations from the tumor and 100 % (4/4) of the revision group were treated with closed reduction. Three patients from the tumor group (2% [3/147] total) experienced a total of three dislocations and one patient four dislocations (< 1% [1/147] total). The first dislocation occurred in 88% of the cases within 5 months following surgery during activities of daily living. 82% of the second dislocations and all third dislocations occurred within 4 months of the previous dislocation. Interestingly, no significant difference was found in the rate of re-dislocation between surgical and non-surgical treatment in either group.

Discussion: Dislocation of a proximal femur tumor endoprosthesis is an early complication following surgery and continues to be a challenging condition to treat, especially in cases with extensive soft-tissue defects. Since 2000, a polyester ligament is successfully used in our institution as a reinforcement to reduce the risk of hip dislocation in proximal femur tumor endoprosthesis. Surgical and non-surgical methods to reduce the risk of hip dislocation are discussed.

Parosteal osteosarcoma is an uncommon tumour. Different methods of surgical treatment have been reported. Aim of this study was to investigate differences in outcome after biological and prosthetic reconstruction.

Since August 1969, 28 patients have been treated at our institution. Average age was 26 years, range 15 to 59 years. Patient data was retrospectively reviewed within the prospective database of the Vienna Tumour Registry. Average follow-up was 133.9 months, range 8.4 to 382.6 months. Two patients died of disease 8.4 and 81.4 months after operation, respectively, another patient died due to unrelated causes 330.4 months postoperatively. All surviving patients were followed for a minimum of 3.6 months.

Location of the lesion was the distal femur (19), proximal humerus (four), proximal tibia (three), mid-diaphyseal and proximal femur (one each). In 12 patients endoprosthetic reconstruction was indicated. Biological reconstruction was performed in 11 patients. Three patients underwent rotationplasty, two patients were amputated. Eight of 12 patients with endoprostheses have been revised, five have had multiple revisions. Causes for revision were bushing wear (four), aseptic loosening (four), infection (three) and periprosthetic fracture (one). There was no local recurrence in the endoprosthetic group. Two of 11 patients with biological reconstruction underwent revision due to pseudarthrosis and femoral fracture, respectively. There were two cases of local recurrence requiring secondary amputation. Two patients with rotationplasty underwent revision for wound healing disturbance and thrombectomy, respectively. Three patients developed lung metastases, leading to death of disease in two cases of amputation and rotationplasty. One patient with endoprosthetic reconstruction was alive 129.0 months after pulmonary metastasectomy. Functional outcome was satisfactory in all patients; there were no significant differences between patients with endoprosthetic or biological reconstruction.

Biological reconstruction showed less revisions compared to endoprostheses, however, exact preoperative planning is required to obtain clear margins of resection.

Fibula autograft reconstruction, both vascularised (v) and non-vascularised (nv), has been established as a standard method in limb salvage surgery of bone and soft tissue tumours of the extremities. This study retrospectively analyses the results of fibula autograft procedures in general and in relation to vascular reconstruction or simple bone grafting.

Since the implementation of the Vienna Tumour Registry in 1969, 26 vascularised and 27 non-vascularised fibula transfers have been performed at our institution in 53 patients, 26 males and 27 females with an average age of 21 years (range 4 to 62 years). Indications included osteosarcoma in 18, Ewing’s Sarcoma in 15, adamantinoma in 5, leiomyosarcoma in 3 and others in 12. Thirty patients were operated for reconstruction of the tibia (8v/22 nv), 7 for the femur (6v/1nv), 7 for defects of the forearm (4v/3nv), 5 for metarsal defects (all v), 3 for the humerus (1v/2nv) and one patient was treated for a pelvic defect (nv).

Average follow-up was 63 months (range 2 to 259 months). 43 patients showed successful primary bony union of the autograft. In 12 cases pseudarthrosis indicated further surgical revision, 9 of these patients were primarily reconstructed by use of a nv autograft. 4 patients, 2 with v and 2 with nv reconstruction, suffered a fracture of the transplant and were operated for secondary osteosynthesis. 10 patients with v bone graft developed wound healing disturbances which led to surgery, 2 patients with nv grafts suffered such complications. In 2 patients recurrent infection of a nv and a v fibula transfer led to the implantation of a modular tumour prostheses or amputation, retrospectively. Function of all patients with primary bone healing was rated satisfactory.

The use of fibula autograft in limb-salvage surgery under oncological conditions allows biological reconstruction with good functional outcome, especially when primary bone healing is achieved. Vascularised bone grafting seems to have a better outcome in terms of primary bone healing than simple fibula bone grafting, and thus represents a feasible choice in the reconstruction of bone defects from tumour resection.

Ten year results of 100 primary lower limb reconstruction prostheses implanted between 1982 and 1989 were analysed. In a Kaplan-Meier estimate there was a 85% three years, a 79% five years and 71% ten years survival rate. Most common reason for implant failure was aseptic loosening in 27% of patients (11 patients; range 10–121 months) after initial operation. Other reasons for revision surgery were implant failure (4) and infection (4). Early repair of prostheses-related minor complications, was polyethylene bushings destruction. After a median followup of 127.5 months after the initial surgery, 51 patients had died and eight patients were lost to followup. Forty-one patients were evaluated clinically and radiologically using the MTS score and the radiologic implant evaluation system of the International Symposium on Limb Salvage. 41 patients had a mean of 80% (range, 40%–100%) of the normal functional capability.

We studied the bone mineral density (BMD) of 48 long-term survivors of highly malignant osteosarcoma who had been treated according to the chemotherapy protocols of the German- Swiss-Austrian Co-operative Osteosarcoma Study Group which include high-dose methotrexate. The mean age of the patients was 31 ± 4.2 years and the mean follow-up 16 ± 2.2 years. The BMD of the lumbar spine and of the proximal femur of the non-operated side was measured by dual- energy x-ray absorptiometry. A questionnaire was given to determine life-style factors, medical history and medication. Ten patients were osteoporotic, 21 osteopenic and 17 normal according to the WHO definition.

Eighteen patients suffered fractures after receiving chemotherapy and all had significantly lower levels of BMD for all the sites measured.

In 251 patients over a period of 15 years an uncemented Kotz modular femoral and tibial reconstruction mega prosthesis was implanted after resection of a malignant tumour of the lower limb. Twenty-one patients (8.4%) underwent revision for aseptic loosening, again using an uncemented prosthesis, and five of these required a further revision procedure. The median follow-up time from the first revision was 60 months (11 to 168) and after a second revision, 33 months (2 to 50). The probability of a patient avoiding aseptic loosening for ten years was 96% for a proximal femoral, 76% for a distal femoral and 85% for a proximal tibial implant.

At the time of follow-up all radiographs were assessed according to the International Symposium of Limb Salvage criteria. The first radiological signs of aseptic loosening were always seen at the most proximal or distal part of the anchorage stem at a mean of 12 months (4 to 23) after the first implantation. Using the Musculoskeletal Tumor Society score for evaluation, the clinical results showed a mean of 88% of normal function.

We treated 106 patients with a peripheral osteoid osteoma by conventional surgical methods; 81 had curettage and 25 en-bloc resection.

The rate of local recurrence after curettage was 12% and after en-bloc resection 4.5%. Postoperative fractures were observed in 3% after curettage and in 4.5% after en-bloc resection.

We compared our findings with those reported in the literature after minimally invasive treatment and concluded that curettage can be regarded as the treatment of choice in patients in whom minimally invasive methods do not offer any advantage, for example, for subperiosteal tumours which are readily accessible, or when the diagnosis is unclear and further histological analysis is required.