Recently, several preliminary reports have been issued on the application of computer assistance to bone tumour surgery. Surgical navigation systems can apply three-dimensional images such as CT and MR images to intraoperative visualization. Although CT is better at describing cortical bone status, MRI is considered the best method for defining the extent of marrow involvement for bone tumours and for planning surgical resection in bone tumour surgery. There have been a few reports on the application of MR imaging to navigation-assisted bone tumour surgery through CT–MR image fusion. However, the CT–MRI fusion technique requires additional costs and exposure of the patient to radiation from the preoperative CT, as well as additional time for image fusion. Above all, the image fusion process is a kind of registration (image to image registration) that inevitably leads to registration error. Herein we describe a new method for the direct application of MR images to navigation-assisted bone tumour surgery as an alternative to CT–MRI fusion.

Six patients with an orthopaedic malignancy were employed for this method during navigation-assisted tumour resection. Resorbable pin placement and rapid 3-dimensional spoiled gradient echo sequences made the direct application of MR images to computer-assisted bone tumour surgery without CT–MR image fusion possible. A paired-point registration technique was employed for patient-image registration in all patients. It took 20 min on average to set up the navigation (range 15 to 25 minutes). The mean registration error was 0.98 mm (range 0.4 to 1.7 mm). On histologic examination, distances from tumours to resection margins were in accord with preoperative plans. Mean duration of follow-up was 25.8 months (range 18 to 32 months). No patient had a local recurrence or distant metastasis at the last follow-up.

Direct patient-to-MRI registration is a very useful method for bone tumour surgery, permitting the application of MR images to intraoperative visualization without any additional costs or exposure of the patient to radiation from the preoperative CT scan.

As a result of lateral skin numbness that quite commonly occurs after knee joint operation, injury of the Infrapatellar branch of Saphenous nerve is often underestimated and regarded as a trivial complications. However, there are many complaints and worries from the patients in relation to the injury of this nerve never seems to stop.

The authors wanted to report the results of preserving this nerve during the unicompartmental knee arthroplasty for preventing lateral skin numbness.

The targets of this study were 100 cases of the unicompartmental knee arthroplasty by a single surgeon. All of the cases were medial compartmental osteoarthritis and in which a minimally invasive technique was used, with the average follow up of two years and eight months (range 24 to 42 months). The results were recorded in terms of classification of the nerve by location, preservation after surgery, sensory changes of the lateral skin flap, and complications. The classification by the location of this nerve was observed as either Mochida Type I with 76 people (76%), Type II with 16 people (16%), and unclassified types with eight people(8%). In Type I, this nerve was saved in 62 cases (82%). However in Type II, it could not be preserved in any cases because of the surgical procedure. The results of our study showed that while most of the nerve (76%) on average had a distance of 9.13mm (range 2 to 19mm) from the medial joint line to the nerve and passed inferiorly. This results allowed us to predict ahead of the location of this nerve and careful incision during the operation can preserve this nerve.

The authors discovered that in cases of unicompartmental knee arthroplasty, the nerve can be easily preserved, as 62 people(82%) of type I had this nerve completely preserved. Even if five extra minutes is necessary in order to preserve this nerve, when we think of the patient’s satisfaction it is thought of as a meaningful procedure.

The purpose of this study in to investigate the role of infrapatellar fat pad on primary total knee arthroplasty. We evaluated 100 patients who had been undergone TKA from August 2002 to July 2003, with open box posterior substituting femoral component implant (Scorpio PS Knee^™). The study was performed prospectively and randomly allocated. We divided two groups. Group 1 (50 knees) was preserved infrapatellar fat pad and repaired fad at wound closure. Group 2 (50 knees) was excised infrapatellar fat pad as possible and repaired only joint capsule. We analyzed and compared clinical results of Knee Society knee (KS) score, function score, patellar score and Insall-Salvati ratio in both groups. The complications of each group were evaluated. Patients were followed up for mean 40 months(17~52 months).

Mean KS score was 91.9 (91.94±5.58) in Group 1 and 90.9(90.92±6.38) in Group 2. Mean function score was 81.6(81.64±13.18) in Group 1 and 83.7(83.79±17.71) in Group 2. Mean patellar score was 29.9(29.89±9.10) in Group 1 and 27.9(27.90±1.80) in Group 2. And mean patellar height as Insall-Salvati ratio was 1.19(1.19±0.17) in Group 1 and 1.23(1.23±0.11) in Group 2. The differences between the Group 1 and Group 2 in all of index were statistically insignificant. In complications, 2 cases of recurrent hemarthrosis were observed in Group 1 patients.

We concluded The difference of clinical outcomes whether infrapatellar fat pad was excised or not were statistically insignificant. However, preservation of infrapatellar fat pad on open boxed PS TKA showed unique complications such as recurrent hemarthrosis which might be caused by fat pad adhesion to intercondylar notch. We propose that infrapatellar fat pad on primary PS TKA with open box design would like to be excised for prevention of unique complications.