A retrospective study focusing on long-term follow up of 28 patients with a malignant bone tumour in the distal femur was conducted. Patients with a mean age of 50 (18–90) were clinically and radiologically followed-up for a mean period of 64 months (7–144). Osteosarcoma was the most common primary bone tumour, occurring in 15 patients. The 5-year survival for all patients was 80,9%. At final follow-up, 19 patients were still alive and had a mean follow up of 74,6 months (7–137).

Clinical evaluation was done with the MSTS questionnaire (mean score: 70,0 (26,7–93,3)) and the use of the TESS (mean score: 82,5 (45–99,2) and SF-36 (mean Physical Component Score (PCS): 46,6 (27,1–56,5), mean Mental Component Score (MCS): 53,7 (range 37,0–62,1) was introduced

There were 12 complications: 5 aseptic loosenings, two deep prosthetic infections, two luxations, one prosthetic fracture and two fissures. Six failures were re-operated. An overall prosthetic survival at 5-years of 77,0 % was found. A total of eight (29%) prostheses were considered to have failed after a mean follow up of 27,4 months (0–97). Risk factors in failure of the prosthetics were: non HA-coated stem and top stem-ratio > 1.2. Not length of the endoprosthesis and base stem-ratio. The top-ratio had a mean value of 1,14 (1,00–1,52) and for the four patients with an aseptic loosening the mean top-ratio was 1,23 (1,12–1,51) which was significantly different (p< 0,05 Mann-Whitney U test).

Our results suggest that of the MUTARS endoprosthesis has a good 5-year survival.

The use with a HA coating is preferable. The use of a stem-cortex ratio (> 1.2) at the top of the prosthetic stem can be predictor for aseptic loosening. The addition of the TESS and SF-36 scores give more insight information in how patients undergo their disease: half do not feel disabled.

Limb-sparing surgery has become the preferred surgical treatment of malignant bone tumours of the knee. In patients with intra-articular extension of their tumour, extra-articular limb sparing surgery can prevent the knee from amputation. In a retrospective study between January 1985 and December 2007, we performed 34 extra-articular tumour resections of the knee-joint for a bone- or soft tissue tumour in the distal femur or proximal tibia with (suspect) intra-articular tumour extension into the knee on MRI. Contra-indications were extension of the tumour into the extensor mechanism and/or tumour involvement of the neurovascular bundle. Osteosarcoma (23/34) was the most common primary malignancy. Mean age was 36 years (17–70) and the mean follow up was 9 years (1–19).

Patient survival rates at 5 years and 10 years are 78% and 58% respectively, mean patient survival was 47 months (8–211). In 12 (35%) patients, the primary implanted prosthesis failed during follow up. Prosthetic survival rates including minor revision surgery were 63% at 5 years and 36% at 10 years. Six (18%) patients had local recurrence of their malignancy, 5 of them in the popliteal fossa. Local recurrence was significantly correlated with marginal margins (P< 0.05). Fifteen patients had major complications (44%) mainly deep infection in proximal tibia resections and aseptic loosening in distal femur resections. Aseptic loosening was significantly correlated with non HA-coated stems (P< 0.05). Functional outcome scores according to MSTS (mean 81, (65–93)) and TESS (mean 85, (56–98)) of survivors are good.

Our results suggest that extra-articular tumour resections of the knee-joint can provide a functional endoprosthesis and can be an alternative for primary amputation. However it is a technical demanding procedure with acceptable local recurrence and high complication rates in patients with, in general, poor survival.