Several preoperative planning tools in computer-assisted surgery in acetabular fractures have been proposed. Moreover, all these preoperative planning tools are based on geometrical repositioning with their own limitations. The aim of this study was to evaluate the value of our prototype virtual planning tool using a rigid biomechanical model to predict failure in fracture reduction.

Between November of 2015 and June of 2016, 10 patients were operated by the main author for acetabular fracture in our institution. To validate our biomechanical model planning tool, biomechanical simulation was performed for each patient immediately after the surgery. Reduction quality was assessed on post-operative CT scans. A 3D model of the acetabular fracture was build out of the CT images using the non-commercial software Itksnap. Then a biomechanical model implemented within the non-commercial Artisynth framework was used to perform virtual reduction. Surgical approach and surgical strategy according to the operative report were simulated. The simulated reductions and the surgical reductions were compared.

The same reductions were obtained during surgery and biomechanical simulation in the 10 cases. For 7 cases, reduction was achieved by anterior surgical approach and so was the simulation. For 3 cases, reduction was achieved by posterior surgical approach and so was the simulation. The biomechanical simulation found similar results using the same surgical strategy with 9 anatomical reductions (90%) and one imperfect reduction (10%). The mean duration to perform acetabular planning surgery was 24 +/− 9 min [16–38].

Our virtual planning tool using a rigid biomechanical model can predict success or failure in fracture reduction according to the surgical approach and the surgical strategy.

Introduction

We report a single-centre, prospective, randomised study for pedicle screw insertion, by using a Computer Assisted Surgery (CAS) technique with three dimension (3D) intra-operative images intensifier versus conventional surgical procedure.

In recent years internal fixation of the spine by using posterior approach with minimally invasive and percutaneous technique were increasingly used in trauma. The percutaneous surgery lose information and navigation is supposed to provide better data because the lost information is found again. We hypothesise that a percutaneous minimal invasive dorsal procedure by using 3D intra-operative imaging for vertebral fractures allows short operating times with correct screw positioning and does not increase radiation exposure.

59 patients were included in this prospective, monocentric and randomised study. 29 patients (108 implants) were operated on by using conventional surgical procedure (CP) and 30 patients (72 implants) were operated on by using a 3D fluoroscopy-based navigation system (3D fluo). In the two groups, a percutaneous approach was performed for transpedicular vertebroplasty or percutaneous pedicle screws insertion. In the two groups surgery was done from T4 level to L5 levels. Patients (54 years old on average) suffered trauma fractures, fragility fractures or degenerative instabilities. Evaluation of screw placement was done by using post-operative CT with two independent radiologists that used Youkilis criteria. Operative and radiation running time were also evaluated.

With percutaneous surgery, the 3D fluo technique was less accurate with 13.88% of misplaced pedicle screws (10/72) compared with 11.11% (12/108) observed with CP. The radiation running time for each vertebra level (two screws) reached on average 0.56 mSv with 3D fluo group compared to 1.57 mSv with the CP group. The time required for instrumentation (one vertebra, two screws) with 3D fluo was 19.75 minutes compared with CP group 9.19 minutes. The results were statistically significant in terms of radiation dose and operative running time (p < 0.05), but not in terms of accuracy (p= 0.24).

With percutaneous procedures, 3D fluoroscopy-based navigation (3D fluo) system has no superiority in terms of operative running time and to a lesser degree in terms of accuracy, as compared to 2D conventional procedure (CP), but the benefit in terms of radiation dose is important. Other advantages of the 3D fluo system are twofold: up-to-date image data of patient anatomy and immediate availability to assess the anatomical position of the implanted screws.

Poor outcome in ACL reconstruction is often related to tunnel position. This study investigates the use of surgical navigation to improve outcome. Improving accuracy of tunnel position will lead to improved outcome.

In a prospective randomised controlled trial 60 ACL plasties with quadruple-loop semi-tendinosus and gracilis tendon were randomised to either standard instrumentation or computer assisted guides to position the tibial and femoral tunnels. The results were evaluated on clinical outcome based on IKDC laxity measurements and radiologic assessment of anterior drawer at 150 and 200N as well as radiological assessment of the tunnel positions.

No complications were observed in either group. IKDC laxity was level A in 22 knees in the conventional group (average 1.5 mm (0-6) at 200N) compared with 26 navigated knees (average laxity 1.3mm (0-5)). Laxity was less than 2 mm in 96.7% of the navigated group (83% in conventional group). The variability of laxity in the navigated group was significantly less than the conventional group, with the standard deviation of the navigated group being smaller than the conventional group standard deviation (p = 0.0003 at 150N and 0.0005 at 200N TELOS).

A significant difference (p=0.03) was found between the groups in the ATB value characterising the sagittal position of the tibial tunnel (negative ATB values imply graft impingement in extension). In the conventional group mean ATB was -1.2 (-5-+4) while it was 0.4 (0 - 3) in Group II. There were no negative ATB values in the Navigated Group.

The use of computer assisted navigation creates a more consistently accurate tibial tunnel position than using conventional techniques. It is suggested that this should reduce impingement and improve graft longevity.

Purpose of the study: We present the clinical and radiologic results of a prospective series of 20 patients who had percutaneous osteosynthesis of the thoracolumbar spine using a longitudinal system with monoaxial screws.

Material and methods: Twenty patients, 12 women, were treated from February 2008 to February 2009. Mean age was 44 years (15–61 years). Fractures were from T4 to L5, five patients had two levels fractured. There were 18 Magerl A and two type B. None of the patients had neurological problems. The reduction was achieved with a postural method and instrumentation with monoaxial screws using the percutaneous longitudinal method. Two levels were instrumented for 12 patients, three levels for three and five levels for four. Vertebroplasty was associated in nine patients. Pain (VAS), vertebral kyphosis (VK), regional angle (RA) were assessed pre-, postoperatively and at last follow-up. Operative time, blood loss, and duration of hospital stay were noted. Pedicle implantations were controlled on the scanner.

Results: Mean follow-up was ten months (3–19 months). In the preoperative phase, the VAS was 7/10, VK 17 (8–26), RA 16.6 (4–30). Postoperatively VAS was 4/10), VK 8 (4–15), RA 10.4 (−3 to 27). AT last follow-up VK was 8.5 and RA 12. Mean operative time was 90 minutes (40–180). On the postoperative scan, 23 of the 106 screws implanted had an extraosseous position (21%) including seven cranial screws. None of the patients developed a neurological deficit postoperatively. The first rise from bed was on day 1 in 14 patients. Mean duration of hospital stay was eight days (6–35).

Discussion: This reduction method provides a gain in VK (−9), a value between orthopaedic treatment (−8 gain) and surgical treatment as reported at the Sofcot in 1995 (−11.1 gain). The reduction was maintained well without loss at last follow-up.

Conclusion: This technique allows assembly of more or less long rigid configurations depending on the injury levels, with satisfactory reduction which is sustained over time. Blood loss is zero with little pain in the postoperative period.

Metal-on-metal hip arthroplasty is nowadays a well spread technique for hip replacement. It is a technically demanding procedure with sine qua non steps. Most of the large Australian, British and north-American clinical outcomes found about 20% early failure, within 3 months, during the steep part of the learning curve. In a biomechanical study on cadaver we showed that valgus and version placements should be appropriate in order to get the most effective strength in compression. But valgus placement is drastically limited by lateral neck notching which leads to early fracture. Anteversion also should be manage to address the cam-type shape of the ventro-lateral femoral neck, since most of the young patient with hip arthritis present retroverted misalignment of the head along the neck axis. The size of the femoral head is another issue because big head component needs a big acetabular cup. Sparing large amount of bone on the femoral side might lead to bone lost on the pelvic side. In order to enhance the placement of the femoral component – smallest one, in valgus, without retroversion and without neck notching – manufacturers propose mechanical device based on neck intraoperative palpation. Digitalized versions of this principle are also available. These systems still demand experienced surgeon to make slight adjustment on entry point and trajectory of the guide-wire. Imageless computer navigation based on proximal femur palpation and atlas is interesting on almost normal bone but could be inaccurate on altered bone, especially cam-type shape. Navigation based on CT scan gives exact 3D information and accurate planning but is still time consuming. Navigation on 2D fluoroscopic view shows good clinical results with only about 20 minutes more than a standard procedure.

We proposed a bone morphing^® procedure with emphasis of surface palpation on head-neck junction to get accurately the personal shape of each femur. Preliminary results on pathological bones showed safe reaming of the head without notching.

Following orthopaedic reconstruction and cranial neurosurgery, spine surgery is now entering its low invasive period. When, in 90’s, computer went routinely available in the surgical field, the main goal was to help surgeons operate on with more accuracy some difficult but standard procedures. The surgery was “computer aided”. The displayed tools on 2D or 3D images allowed surgeons to avoid permanent intra operative landmarks. Once patient personal anatomy was capture into the machine and the tools calibrated, the surgeon was able to plan and optimised ideal trajectories without direct vision to check tools position. “Navigation” starts to be more obvious to describe this intra operative control. Anyway, we still needed large exposure to get the full bone surface in order to build a 3D surface based model. This model optically localised was matched using rigid or elastic algorithm with preoperative CT scan model or bone morphing^®. Ultrasound recognition of the soft tissue/bone interface let think about trans cutaneous palpation. However, automatic segmentation of the bone surface never lead to commercially available soft. Only X-ray is commonly use during surgery to help surgeon to see tools and bone without surgical exposure. Fluoroscopy allows percutaneous trajectory as iliosacral screwing, vertebroplasty, fracture nailing et caetera. Radiation exposition could therefore be an issue for patient but also for surgeon. Fluoronavigation is a good response to percutaneous surgery. In spine no transversal view could be available. Surgeons should make mental reconstruction of the volume to perform the right trajectory. Industrial proposed intra operative tomography on C-arm with 3D reconstruction. It works well for limbs, but in thoracic and lumbar spine the large amount of surrounding soft tissues leads to low quality images. Flat panel X-ray receptor are a path to get more accurate images. Other perspectives are circular intra CT scan. The cost and the volume of machines stops the spread of such device.

Robots are used by knee surgeons but abandoned by hip surgeons. In spine tool holder robot are available in order to place a pedicular drill guide. Matching with bone is based on fluoroscopy.

Spine navigation could be useful to e-leaning and simulators too. The training of percutaneous surgery is long, because of mental matching between fluoroscopic 2D projections and the vertebra volume. We need a simulator allowing 3D virtual trajectory checked on AP and lateral view to short the learning curve.

Purpose of the study: Anterior cruciate ligament (ACL) navigation systems are based on two underlying principles: «statistical» anatomic position and isometric anatomic (anatomometric) positioning. The purpose of this study was to demonstrate that an anatometric positioning of the transplant can be achieved, in other words, that the transplant can be positioned in the original anatomic air of the ligament insertion while preserving an optimal isometry without notch impingement. This study was also conducted to compare conventional systems with a computer-assisted system.

Material and methods: This study was conducted on thawed fresh-frozen cadaver knee specimens with > 120° flexion. The computer-assisted protocol for ACL surgery was applied to ten knee specimens. The original anatomic insertions of the ACL were dissected then inserted at the appropriate points into the computer display. The tibial and femoral insertion points of two classical aiming devices were recorded. These points were compared with the original anatomic insertion.

Results: For the tibia: classical aiming methods proposed a point of insertion posterior to the anatomic insertion for eight knees and within the frontiers of the anatomic insertion for two, in line with the anterior border of the posterior cruciate ligament. The computer-designated point of insertion for the tibial fixation was always within the anterior third of the ACL insertion, generally medially. For the femur, the transition (or isometric) line ran across the anatomic femoral insertion in all knees. It was observed that in all cases, the surgeon could choose an anatomic insertion with lesser anisometry by situating the insertion in the distal part of this line: for nine knees, the computer-designated femoral point was anatomic and with lesser anisometry. The Acufex aiming device produced better anisometry (my=4 mm) than the Arthrex device (my=6 mm) but with a less favorable anisometry curve.

Discussion: The notion of anatometry is compatible with computer-assisted surgery. This study demonstrated that the computer-designated tibial point of insertion is more anterior and medial than the conventional aiming points. This is a potential choice if the absence of a notch impingement can be visualized: Howel described a manual fluoroscopic method. In our opinion, at the present time, optimal choice of the femoral point to achieve the desired anisometric curve is strictly operator-dependent.

Purpose of the study: Prenatal screening and search for risk factors has lead to early diagnosis of congenital hip dysplasia. The percent of excentration of the dysplastic hip can be quantified with ultrasonography. The purpose of this study was to evaluate the usefulness of ultrasound monitoring of confirmed hip dysplasia as a method for determining the appropriate time to discontinue treatment.

Material and methods: We collected a series of patients presenting unstable hips one month after birth. Ultrasonographic examinations were performed to quantify the instability. Initial treatment was forced abduction. If the infant’s weight was greater than 5.6 kg, a Pavlik harness was used. Physical examination and control ultrasound examinations were performed at 4, 8 and 12 weeks. Forced abduction and ultrasound surveillance were discontinued when the percent of acetabular cover was greater than 50%. Long-term surveillance consisted in physical examination and plain ap view of the pelvis at four months and at onset of walking.

Results: Ultrasound monitoring was instituted for 71 hips in 51 patients. Mean age at onset of the monitoring scheme was 37.7 days (range 38–74 days). Mean acetabular cover, as evaluated by ultrasound before treatment, was 35.5% (range 20–45%). After four weeks, mean cover for 42 hips was 54.7% (range 50–85%). For the other 29 hips, mean acetabular cover was 41.4% (range 36–47%) at four weeks. At eight weeks, 26 of these 29 hips had a mean cover of 60% (52–85%). Acetabular cover remained below 50% for three hips at twelve weeks. Mean HTE at four months was 20.7° (range 10–26°). At walking, all hips were centered and no irregularities were noted on the x-rays of the femoral nucleus.

Discussion: The majority of infants with unstable hips diagnosed at birth achieve spontaneous cure without treatment. For others, cure can be achieved with forced abduction but with a risk of osteochondritis. In our study, ultrasound monitoring enabled a reliable assessment of the proper moment to interrupt treatment.

Conclusion: Ultrasound examination of the hip joint is a satisfactory method for monitoring hip dysplasia in infants aged less than four months. It appears to be useful for determining the moment to interrupt treatment.

Purpose of the study: We describe a surgery navigation system based on virtual fluoroscopy images established with a 3D optic localizer. The purpose of this work was to check the accuracy of the system for posterior spinal implants in comparison with conventional surgery. Duration of radiation and duration of surgery were compared.

Material and methods: A 3D optic localizer was used to monitor the position of the instruments in the operative field, as well as the fluoroscopy receptor. The surgeon took two views, ap and lateral, with a total exposure of two seconds. The C arm was then removed. After image correction, the ap and lateral views were displayed on the work station screen where the computer superimposed to tools on each image. Twenty osteosynthesis procedures for implantation of pedicular screws via a posterior approach to the thoracolumbar spine were performed with this virtual fluoroscopy technique (20 patients, 68 screws). During the same study period, twenty other procedures were performed with the conventional technique (ap and lateral x-ray with the C-arm after drilling the pedicle, 20 patients, 72 screws). The position of the spinal implants was compared between the two series on the ap and lateral views and postoperative CT. Similarly time of exposure to x-rays and duration of the surgical procedure were recorded.

Results: The rate of strictly intrapedicular implantation was less than 8% (5/68 screws) in the virtual fluoroscopy series versus 15% (11/72 screws) in the conventional series. Time of exposure to radiation was significantly lower in the virtual fluoroscopy series with a 1 to 3 improvement (3.5 s versus 11.5 s on average) over the conventional method. With training, this method is not more time consuming (10 min per screw for the conventional method versus 11.25 min for virtual fluoroscopy).

Discussion and conclusion: Compared with conventional fluoroscopy, the virtual technique enables real time navigation while significantly reducing the dose of radiation, both for the patient and the surgery team. There are two types of advantages of virtual fluoroscopy over CT-based systems: first virtual fluoroscopy is immediately available without specific preoperative imaging and secondly it provides real non-magnified images acquired once during the procedure, after which the C-arm is removed. 3D virtual fluoroscopy is probably the next step but requires further experience.

Purpose of the study: Appropriate treatment of displaced supracondylar fractures of the distal humerus in children remains a controversial topic. Blount reduction followed by percutaneous or open pin fixation have been widely used. The purpose of this study was to analyze outcome after open surgical treatment of these fractures in pediatric trauma victims.

Material and methods: The study included all pediatric patients who underwent surgical treatment for displaced supracondylar fractures of the distal humerus over a ten year period. Fractures were classified III or IV according to Lagrange and Rigault. Cross pinning was used in all cases, via a posterior approach or a double lateral and medial approach. The mechanism of the fracture and pre- and postoperative vascular and neurological complications were noted. The long-term assessment included standard x-rays of the elbow joint (ap and lateral views) and a physical examination to search for misalignment and residual neurological disorders.

Results: We identified 110 patients, 61 boys and 49 girls, mean age 7.61 years (range 2–15 years). There were 96 grade IV fractures and 24 grade III. Mechanisms were: sports accident (n=44), fall from height (n=36), fall from own height (n=30). A neurological complication was observed in 29 children, skin opening in three and regressive vascular damage in six. A posterior approach was used for 95 patients and a double approach for 15. There was one revision for secondary displacement. Five patients developed transient paresthesia of the ulnar nerve which resolved without sequela. Three patients presented a moderately hypertrophic or deformed callus which had little functional impact. One patient with an open fracture required surgerical arthrolysis for stiffness six months after fracture.

Discussion and conclusion: Open surgery is a very reliable treatment for supracondylar elbow fractures with a low rate of short- and long-term complications. Ulnar nerve palsy, the classical complication of percutaneous cross pinning, can be attributed to the medial pin (7–16% of cases in the literature). The Blount method and Judet or Métaizeau fixations can sometimes be complicated by secondary displacement or a deformed callus, complications which were almost never observed in our series. The results obtained in this series favor our approach for open surgery for the treatment of displaced supracondylar fractures of the distal humerus in children.

Purpose: The purpose of this work was to study the reliability and the precision of a lumber vertebra reconstruction method using images obtained from a 3D statistical model and two calibrated radiograms. The technique is designed for surgical approach to the lumbar spine and implantation of osteosynthesis material using enhanced-reality technology.

Material and methods: A lumbar vertebra was reconstructed on several specimens using images issuing from a 3D statistical model and two calibrated radiograms. The images obtained from the model of this lumbar vertebra to be reconstructed constituted the preoperative images. Intra-operative images corresponded to two calibrated radiograms acquired with a fluoroscope using advanced technology (silicium receptor). The model was equipped with reflecting patches which can be detected in space using a 3D optical system. Correspondence between the 3D statistical model and the two calibrated radiograms was achieved with appropriate software. Navigation views were displayed on the screen to guide surgical tools at the vertebral level. Pedicular screws were implanted into several anatomic specimens to evaluate the reliability and precision of the system. The exact position of the implanted screws was established with computed tomography.

Results: This system demonstrated its reliability and precision for the reconstruction of a lumbar vertebra from a 3D statistical model and two calibrated radiograms. All the implanted screws were perfectly positioned in the pedicles. Precision was to the order of 1 mm.

Discussion: This method is a passive system not requiring intraoperative intervention. Reconstruction of a lumbar vertebra from a preoperative 3D statistical model and two intra-operative calibrated radiograms avoids the need to identify anatomic landmarks and/or surface points on the vertebra to be reconstructed. The level of precision is very similar to that obtained with CT-based systems. Preoperative CT is not needed for navigation.

Conclusion: With this system, new generation fluoroscopic equipment should appear in the operating room, allowing acquisition of successive calibrated images. The digital data could then be matched with statistical anatomic data, avoiding the need for preoperative imaging (CT or MRI). Progressive introduction of intra-operative ultrasound to replace the calibrated radiograms should open a new approach for percutaneous surgery of the lumbar spine.

Purpose: This study analysed nerve trunk injury associated with posterior fractures of the pelvic girdle, distinguishing initial post-trauma damage from morbidity correlated to treatment by reduction and iliosacral screw fixation.

Material: Fifty bone or ligament injuries to the posterior pelvic girdle were identified in 44 patients. Management included initial external reduction and differed fixation using iliosacral screws inserted under fluorescence guidance.

Methods: The metameric examination of the lumbar and sacral trunks (L2, L3, L4, L5, S1, S2, S3) was performed at admission when the patient was conscious. The postoperative work-up included a complete neurological exam and computed tomography assessment of the screw trajectory. The quality of the reduction was quantified on the anterioposterior view of the pelvis. At last follow-up, evolution of symptoms ± EMG, Trendenburg gait, Mageed score, QMS score and pain (assessed on a visual analogue scale) were recorded.

Results: Preoperatively, 14 deficits of the nerve trunks were identified. The neurological status was unknown for eleven bone and ligament injuries because the patients were sedated at admission. Postoperatively, 28 deficits were identified. Fourteen (50%) involved the lumbosacral trunks L4 and L5, five the S1 root, six L4, L5, S1 territories, and three L5 to S4.

Computed tomography demonstrated 15 extraosseous screws lying anteriorly to the sacral ala or in the sacral canal. These extraosseous screws were associated with neurological deficits in nine cases without a preoperative diagnosis. In six cases, the extra-ossesous screw was not associated with any postoperative deficit. In five cases, neurological lesions diagnosed after the operation were not associated with an extra-osseous screw. Twenty-six neurological lesions were reviewed at a mean follow-up of 25 months: improvement was observed in 19, no change in five and aggravation in two.

Conclusion: Initial diagnosis of neurological injury with precision of the localisation can be established for only half of pelvic girdle fractures. The main mechanism involves stretching of the lumbosacral trunk by displacement of the sacral ala. Injury to the superior gluteal nerve is often associated. Closed reduction or compression of a nerve trapped in the fracture gap during screw fixation could be a second mechanism. Finally, rigorous screw insertion is necessary to avoid extra-osseous trajectories lying anteriorly to the sacral ala.

Purpose: Injury of both cruciate ligaments raises difficult therapeutic problems in trauma victims. The severity of such lesions is related to the context of multiple trauma and to the general regional context associating vascular and neurological injury. Therapeutic management should be multidisciplinary to determine the appropriate strategy. Orthopaedic treatment should take into account the different diagnostic and therapeutic aspects. The purpose of this work was to detail ligament injuries observed and to assess results of treatments proposed.

Material and methods: This retrospective series included 20 patients (14 men and 6 women), mean age 33 years (18–54). Five had multiple trauma with head injuries and multiple fractures. The initial diagnosis was traumatic knee dislocation in 14 patients. Seven patients underwent emergency vascular explorations with subsequent femoropopliteal bypass (n=3). Neurological lesions included three cases of complete section of the lateral popliteal sciatic. Orthopaedic treatment was used in three cases. We used external fixation for two months on the average in three patients. Six others underwent surgery (less than eight days after injury) after obtaining an MRI. The surgical strategy was based on several arguments: age, general status, level of the ligament injury. Three patients underwent secondary surgery on the anterior cruciate ligament. Outcome was assessed at a mean follow-up of 36 months (20–60). The clinical assessment of the objective result was based on frontal and sagittal laxity. The subjective result and the level of sports activities were also recorded. Radiographically, we studied the standard x-rays in single leg stance and also the stress images using telos with anterior then posterior drawer.

Results: Excepting one case of amputation necessary due to the vascular and nervous injuries, orthopaedic treatment allowed an acceptable functional result in sedentary patients: good frontal stability and minimal anteroposterior residual laxity. Fourteen athletes underwent emergency surgery to repair the posterior cruciate ligament: posterior approaches in eight knees with injury of the floor with no posterior drawer at last follow-up; anterior approaches in six knees for suture of the posterior cruciate ligament and insertion of a synthetic ligament tutor with anterior cruciate ligament repair during the same operative time (two floor reinsertions, one patellar tendon plasty, and three Cho plasties). The stability of the posterior pivot was excellent but the tibial reinsertions of the anterior cruciate ligament failed. Seven knees required mobilisation under general anaesthesia 2.5 months later. Three knees underwent secondary anterior cruciate repair using the Kenneth Jones technique with negative Lachmann at last follow-up.

Discussion: Excepting vascular and neurological emergencies dictating the initial therapeutic attitude, our orthopaedic management was based on a detailed identification of the lesion using emergency MRI: anterior or posterior approach, anterior cruciate repair technique dependng on association with peripheral ligament injury. Good results in terms of posterior laxity were achieved in this series, confirming the importance of emergency repair of the posterior cruciate. If the medial ligaments are intact, the anterior cruciate can be repaired in the emergency setting with a Cho plasy. In other situations, we prefer waiting before surgical repair of the anterior pivot.

Purpose: No conventional surgical technique for ligament reconstruction can be used in all cases to achieve ideal position of the transplant. Navigation systems without visualisation of the anterior cruciate ligament should meet the requirements. This is an operative strategy based on one or more computer assisted procedures enabling ligament reconstruction without the need for conventional pre- per, or postoperative imaging. The principle is based at the present time on the use of a station (computer, localisers, display screen, command pedal) used for processing data (spatial measurements and positioning) delivered by markers fixed on rigid bodies and tools (palpation, aiming tools).

Material and methods: This study was conducted on ten cadaver knees. Each knee was instrumented with the station. Joint kinetics were recorded with and without the ACL and after harvesting the transplant: patellar ligament and hamstring ligaments. Bone morphing was used to draw the tibial and femoral surfaces. Two types of aiming tools were tested by recording the data points issuing from the tibial output and the femoral input. The position of the femoral and tibial holes was determined to achieve the smallest anisometry and absence of notch conflict. Isometric zones were compared with the anatomic zones of the ACL. We also compared the position of the transplant determined by the computer and that determined according to the methods of conventional arthroscopy. An x-ray of each knee was obtained to compare with data in the literature concerning the advised position of the femoral and tibial holes with that established by the computer navigation system. Each knee was tested with KT1000 before and after surgery.

Results: The precision of bone morphing was 0.1 mm. Anisometric curves were compatible with drilling holes calibrated to the size of the implant in four knees. The operator used the navigation system to determine the point of the femoral hole in six knees. The system then calculated the point of the tibial hole automatically eliminating the risk of notch conflict. The anisometric values were less than 2 mm; the distance roof of the notch/anterior border of the transplant was calculated as a function of the radius of the transplant (3.5–5 mm). The position of the tibial hole given by the computer system was always more medial than that given by the tibial aiming tools. The position of the femoral tunnel was always more anterior than that given by the femoral aiming tools. The postoperative KT1000 values were identical to the preoperative values.

Discussion: Navigation without visualisation of the ACL is able to position the ACL in an isometric plane or better in an “anatomometric” plane, to inscribe the joint orifice of the tibial hole on the projection of the anterior arch of the notch on the tibial surface, to draw in real time the isometric femoral map on the notch in order to centre the joint orifice of the tibial hole as well as the corresponding laxity map, to indicate on the femoral notch the point which will be the centre of the joint orifice of the femoral hole, to draw the isometric curve of a given fibre and its corresponding laxity map, and to detect and allow the treatment of any transplant-notch conflict.

Purpose: The purpose of this work was to compare the precision and reliability of screw fixation using two different guiding systems. The first system was based on computed tomography (CT) imaging and the second on digitalized fluoroscopic imaging.

Material and methods: Between 1998 and 2000, 88 patients underwent spinal fixation for diverse disease states (idiopathic scoliosis in 43, and fracture, spondylolisthesis or instability in 45). Pedicular screws (n = 223) were inserted in levels T4 to S1. The passive CT navigation system was used for 73 patients (177 pedicular screws) and the fluoroscopic navigation system for 15 (46 pedicular screws). An independent observer identified the position of the pedicular screws on the postoperative CT.

Results: Among the 73 patients who underwent a CT-guided procedure (177 pedicular screws) the rate of incorrect screw position was 6.2% (11/117) with = 2 mm penetration of the cortical. Among the 15 patients who underwent a fluoroscopy-guided procedure (46 pedicular screws), the rate of incorrect screw position was 17% (8/46) again with = 2 mm penetration of the cortical. For scoliosis patients, the rate of erroneous screw insertion was 6% for CT navigation and 28% for fluoroscopic navigation. For fractures and degenerative instability, the rates were 6% and 11% respectively.

Discussion: The passive nature of the two navigation systems used do not induce any peroperative constraint on the surgeon. With the CT system, landmarks have to be collected peroperatively on the posterior arch of the operated vertebra, a step that is not needed for the fluoroscopic system. The two techniques appear to be reliable for insertion of pedicular screws. We did not have any neurological disorders in this series. It can be recalled that the conventional method produces a 15 to 40% rate of erroneous insertion. The CT system provides better results for all types of diseases; the improvement is about 6%.

Conclusion: With CT-navigation, a large portion of the per-operative radiographs are no longer necessary. Operative time is slightly longer than for the classical procedure due to the collection of the 3D information, particularly important for scoliosis. With the fluoroscopy system, no special preoperative imaging is required. Two or three peroperative radiographs are sufficient, limiting irradiation during insertion of the pedicular screws. The fluoroscopic system does not however provide 3D images.

Purpose: This prospective comparative study examined the two-year results of two femoral fixation method for anterior cruciate ligament (ACL) repair using the four-part hamstring technique. A consecutive series of 60 patients with the same tear criteria involving the ACL alone were randomly assigned to the two treatment arms. Femoral fixation was achieved by mixed corticocancellous transfixation or by interference screw fixation.

Material and methods: The series included two cohorts of 30 patients each. We excluded patients with a history of ligament or bone surgery and those with associated lesions of the peripheral ligaments. Complementary lateral reinforcement was not performed in either group. The interference screw fixation group had 20 men and 10 women, mean age 29 years (14–48), 18 right side. The blind femoral tunnel was drilled arthroscopically. The transfixation group included 19 men and 11 women, mean age 26 years (16–40), 17 right side. The blind femoral tunnel was drilled via a transtibial approach using the Rosenberg aiming procedure. In both cohorts, tibial fixation of the transplant was achieved with a resorbable polylactic screw measuring at least the diameter of the tibial tunnel. Statistical analysis of results (Statview 4.5) was based on the clinical IKDC score, thigh volume, and level of sports activity. Telos at 15 and 20 kg was used to measure laxity.

Results: Mean delay to review was 24 months (22–26). The two cohorts were comparable preoperatively (laxity, sports level, meniscal or cartilage lesions). There was no statistical difference for joint amplitudes, joint instability, or level of sports activity at last follow-up. The telos differential laxity at 15 kg was statistically lower in the interference screw fixation group (mean 1.1 mm) than in the transfixation group (mean 1.4 mm) (p < 0.01). There were no complications in either group, particularly no cyclope syndrome. Radiographically, there was no statistical difference for the position of the tibial tunnel. The femoral tunnel was however different: the Aglietti index was 0.57 for transfixation and 0.62 for interference screw fixation (p < 0.01).

Discussion: This prospective study demonstrated the good mid-term anatomic results after 4-part hamstring plasty of the ACL for both types of femoral fixation (transfixation or interference screw fixation). The position of the femoral tunnel appeared to be better with interference screw fixation, with a statistical correlation with better anatomic results (telos). This suggests that the transtibial femoral aiming procedure does not necessarily produce a totally satisfactory isometric alignment.

Purpose: We present a prospective review of 30 unstable pelvic ring fractures treated with iliosacral screw fixation under fluoroscopic guidance with or without anterior osteo-synthesis.

Material and methods: Thirty patients were included between January 1997 and June 2000. They were all treated in an emergency setting by traction with or without a pelvic clamp. Osteosynthesis was deferred for a mean eight days. Percutaneous iliosacral screw fixation was used in all patients associated with symphsis osteosynthesis in eight. The radioscopic technique used three views: inlet, outlet and lateral. There were three Tile B fractures, 26 Tile C fractures and one sacral fracture. The ISS was 30.8/75. Eleven patients experienced haemorrhagic shock, 16 had injuries to the lower limbs, four had surgical urological injuries, and seven had emergency arterography. A neurology examination and CT scan were obtained pre- and postoperatively. Clinical assessment used a visual analogue scale, the Majeed score, and the WHO score. Peroperative radiation was quantified in minutes, Kvots and mA.

Results: Fifty-one screws were implanted, 24 patients with two screws. There were 12 outside the bone and seven potentially iatrogenic lesions among the 18 neurological lesions observed. Mean radiatio was 1.03 min per patient and 0.6 min per screw. Mean follow-up was 24 months (9–50). Clinically the mean scores were: Majeed 8.5/100, WHO 0.7/3, visual analogue scale 3.2/10). Twenty patients suffered pain related to associated injuries. There were three dismantelings including one requiring revision surgery. Deformed callus was: anterior vertical translation 2.9 mm, posterior vertical translation 4.5 mm and horizontal anterior translation 3 mm. There was one complication for the symphysis fixation.

Discussion: These results are comparable to those reported in the literature. Complications are less frequent with this method. External reduction is good when achieved early. This series represents a learning curve where the 12 screws in extraosseous positions occurred during our first 16 cases. Implanting two screws per articulation increases the risk of extraosseous screws. Screw insertion is safer with the lateral view.

Conclusion: This series demonstrates that iliosacral percutaneous screw fixation is a valid method for the treatment of severe fractures of the pelvic ring. The rigorous method required is emphasised.