Fluoroscopy equipments have enabled us to perform operations that otherwise would be impossible but only at the expense of exposing the patients and theatre staff to radiation. The aim of this study was to determine the average radiation exposure to the patients in dynamic hip screw (DHS) fixation, cannulated hip screw (CHS) fixation, intra-medullary nailing (IMN) of femur and tibia operations. The records of all patients undergoing the above operations between May 2000 and August 2003 were retrospectively reviewed. A total of 670 patients were included. 389 had DHS, 85 had CHS, 125 had IMN of femur and 71 had IMN of tibia operations. The average radiation time was 0.7, 1.1, 2.5 and 2.1 min and the average radiation dose (in dose area product-DAP) was 196, 356, 548 and 125 cGy cm 2 for DHS, CHS, IMN of femur and IMN of tibia, respectively. Compared to the registrars, radiation time and dose were higher with the consultants in DHS fixation ( P = 0.02, 0.02). The radiation dose was higher with the senior house officers compared to the registrars in CHS fixation ( P = 0.03). There were no significant differences between the consultants and the registrars in IM nailing operations. The study concludes that radiation exposure to the patients in DHS and CHS operations depends on the experience of the surgeon but not in IMN operations. The IMN of femur involved more than four times higher radiation than IMN of tibia and the CHS fixation involved double the radiation than the DHS fixation. The radiation time was poor comparative metric to estimate radiation dose.

The Phantom based Computer assisted orthopaedic surgical system (CAOSS) has been developed collaboratively by the University of Hull and the Hull Royal Infirmary, to assist in operations like dynamic hip screw fixation. Here we present summary of our system. CAOSS comprises a personal computer based computer system, a frame grabber with video feed from a C-arm image intensifier, an optical tracking system and a radiolucent registration phantom which consists of an H arrangement of 21 metal balls. The phantom is held in position by the optically tracked end-effector. Knowing the optical position of the phantom, a registration algorithm calculates the position of C-arm in coordinate space of the optical tracking system. Computer based planning uses an anteroposterior (AP) and lateral image of the fracture. Marks are placed on the 2D projections of femoral shaft, neck and head on the computer screen, which are then used to create 3D surgical plan. The computer then plans a trajectory for the guide wire of DHS. The depth of the drill hole is also calculated. The trajectory is then shown on both AP and lateral images on the screen. CAOSS meets all the requisite of electrical and electromagnetic radiation standards for medical equipment. There has been extensive validation using software simulation, performance evaluation of system components, extensive laboratory trials on plastic bones. The positional accuracy was shown to be within 0.7mm and angular accuracy to be within 0.2°. The system was also validated using Coordinate Measurement Machine. Our system has the unique feature of the registration phantom which provides accurate registration of the fluoroscopic image.

Image intensifiers are widely used in orthopaedic trauma surgery. Since beginning of fluoroscopy use, concerns have been raised regarding the radiation risks to the patients and the theatre staff in these operations. The radiation risks are classified into two types, stochastic and deterministic risks. Effective dose (ED) and skin dose (SD) values were derived from dose area product (DAP) values and used to quantify the stochastic and deterministic risks, respectively. Patients (670) who had dynamic hip screw (DHS) fixation, cannulated hip screw (CHS) fixation, intra-medullary nailing (IMN) of femur and tibia were included in the study. ED values were 0.3, 0.6, 0.9 and 0.01 mSv and stochastic risks were 3 × 10−5, 6 × 10−5, 9 × 10−5 and 1 × 10−6 for DHS, CHS, IMN of femur and IMN of tibia, respectively. Maximum SD values were 36, 65, 100 and 46 mGy which were only 2, 3, 5 and 2% of threshold dose for temporary skin erythema (2 Gy) in DHS, CHS, IMN of femur and IMN of tibia operations. The radiation exposure in these operations was very low compared to common intervention radiology procedures. The study concludes that the risk of radiation injury in lower limb trauma surgery is extremely small. The radiation doses to patients are within maximum permissible dose (MPD) limits recommended by International Commission on Radiological Protection.

The use of the C-arm fluoroscope for surgical navigation in various Computer Assisted Orthopaedic Surgery Systems (CAOS) has been an important success of research into CAOS technology. To use the fluoroscope for quantitative surgical navigation involves calibrating its 2D images and tracking the spatial position of the fluoroscope's image beam. This allows 3D reconstruction of anatomy from a series of 2D fluoroscopic images. This paper presents a new technique for determining the C-arm position and calibrating the image beam. This technique is based on a small imaging phantom that is placed close to the patient. This paper also briefly describes the CAOS system developed at Hull that uses this imaging phantom and reports on in vivo and in vitro studies.

The difficult part of the intramedullary (IM) nailing operation of long bone is to insert the distal locking screws. The current technique to insert these screws uses numerous fluoroscopic images and depends on skills and expertise of the surgeon. A Computer-Assisted Orthopaedic Surgical System (CAOSS) has been developed collaboratively by the University of Hull and the East Yorkshire Hospitals NHS Trust to assist the orthopaedic surgeons in these operations. The laboratory based test results for insertion of distal locking screws in intramedullary nailing procedure are presented and discussed in terms of accuracy and as part of the validation process to introduce new CAOS procedures into clinical use. This study shows that CAOSS in IM nails is robust and reliable. The positional accuracy in planning the trajectory for insertion of the distal locking screws was shown to be within 0.3 mm and angular accuracy within 0.2°.

A total of 125 consecutive hip fracture patients were investigated regarding hip geometry. There were 33 men of mean age 76 ± 10 years, and 92 women of mean age 78 ± 9 years. Patients with previous hip surgery were excluded. Hip geometry (hip-axis length, width of collum femoris, and femoral shaft and neck-shaft angle) were registered on both plain radiographs and DEXA scans performed within 2 weeks after fracture. On the radiographs, the calcar femorale, the Singh index, and the femoral neck index (FNI) were also calculated and compared with earlier published values of bone mineral density hip in the hip fracture patients. The fracture cases were compared with controls, 192 DEXA scans and 163 radiographs, in patients without hip surgery or known hip disease. As measured on the DEXA scans we found a wider collum femoris and a wider femoral shaft in both the male and female fracture cases, compared to controls. Also, the fracture cases showed signs of osteoporosis as measured by the calcar femorale, the Singh index, and the femoral neck index. These measurements showed good correlation with bone mineral density of the hip as measured by the DEXA scans.