There are many reports in the literature about the benefits of computer-aided surgery with regards to improved limb alignment, reduced blood loss and embolic events but surgeons remain sceptical about its routine use because of availability, cost and time implications. To maximise these benefits and overcome the distractions, a modified navigation technique has been developed after evaluation of the standard measurements.

The true varus/valgus angle of the distal femoral cut achieved with navigation is unknown but represents presumed accurate alignment with regards to the mechanical axis through the femoral head. With placement of the femoral tracker in the medial supracondylar region clear of the intramedullary canal, the navigated cut was correlated with the cut placement determined with the standard intramedullary jig in 10 patients undergoing knee replacement. In addition, jigged femoral rotation was checked with the tracker placement. Tibial slope, varus/valgus angle and rotation were determined using surgeon placement of an external alignment jig and confirmed with tracker placement.

The navigated distal femoral cut ranged from +3 degrees to −2 degrees when measured against the distal cutting block stabilised over an intramedullary rod. The femoral rotation was within 1 degree of the trans-epicondylar line as outlined by navigation when a 3 degree externally rotated jig was used. All of the tibial measurements were within 0.5 degrees of the navigated planned positions.

The femoral cuts are presumed to be accurately determined with navigation as judged from long-leg alignment x-rays but this study highlights the potential error if a fixed valgus cut angle with alignment jigs is used. Tibial preparation, however, was accurately predicted by the surgeon using a traditional external alignment jig. Bone preparation time was reduced to 4 minutes (modified technique) compared to 12 minutes (full navigation, p< 0.05).

With this information, computer-aided navigation is now routinely used to determine the distal femoral cut only and an external alignment jig is used for tibial preparation without navigation. The reduction in blood loss and embolic events and improved limb alignment is now achieved with a reduction in preparation time over full navigated techniques. Use of the pinless surface mounted femoral jig alone highlights these advantages further.

Purpose: The authors would like to report the outcome following evaluation of surgical treatment for acetabular fractures with more than 10 years follow-up.

Materials and methods: 133 consecutive patients were evaluated with 10–16 years post surgery follow-up (mean 12 years). Mean age was 34 years (17 to 70 range) and male: female were 2:1. 90% of our cases were tertiary referrals. The follow-up assessments included AP pelvis and Judet view radiographs and clinical evaluation was performed with the Harris hip score, Modified Merle d’Aubigne score and the SF 36v2 health survey.

Results: Fracture reduction was anatomical in 69% of the patients and in 31% it was non-anatomical. The reduction of the acetabular fractures was considered anatomical when all five lines on post-operative radiographs were corrected and the hip was congruent. Among our patients, 19% had excellent clinical results according to the modified Merle d’Aubigne Score and 58% according to the Harris Hip Score. A poor clinical outcome was identified in 18% of our patients according to the modified Merle d’Aubigne Score and 23% according to the Harris Hip Score. Radiographic evidence of osteoarthritis was in 35,8% of our patients (all grades of arthritis). 6 of our patients had neurological complications (sciatic nerve palsy) (3 pre-operatively, 2 post- operatively and in one patient there was a delayed sciatic nerve palsy secondary to haematoma). In 7 patients (8.6%) there was heterotopic ossification but in only three that was clinically a problem. Two patients developed intraoperatively pulmonary embolism. We had no post-operative deep vein thrombosis or pulmonary embolism.

Conclusions: Our results compare favourably with those of previous published studies with shorter follow-up period. Anatomical fracture reduction is mandatory and improves the clinical outcome. Infection and avascular necrosis are associated with poor clinical outcome. Early surgical intervention for displaced acetabular fractures can improve the final outcome.

Purpose: The authors would like to report a technical innovation in cemented hip arthroplasty. The new device, a “rim cutter” (patent pending) was designed in Exeter and aims at improving the surgical technique of insertion of cemented sockets. The principle aim of this innovation is to cut a rim around the periphery of the acetabulum to a set depth so that the flange of the socket seats into this rim and thus by sealing the space underneath the flange, there is a sustained rise in cement injection pressure behind the socket during implantation. This, improves cement macro and micro interlock, creates a congruent cement mantle with no radioluciencies, especially in the highly predictive DeLee-Charnley Zone I.

Materials and methods: A retrospective clinical study was performed in order to assess the radiological result of the use of the rim cutter. Two groups of patients with 30 in each group (consecutive cases) were enrolled in the present study. In group A, the rim cutter device was used while in group B, the acetabulum was prepared without the use of the rim cutter. In all cases an Exeter contemporary cup and stem were used. All cases were evaluated with postoperative radiographs which were analysed to record the anatomic measurements with regard to:

i) centre of rotation of the socket (COR),

These values were compared with the equivalent measurements made for a normal contralateral hip. In addition to these measurements, any radiolucent line in any zone was recorded. The post-operative film was templated using Orthoview (TM, Southampton, Hampshire) software, which is a digital X ray templating system.

Results: The group where the rim cutter was used showed significantly improved radiological parameters. In this group (group A) the socket was placed closer to the normal centre of rotation (COR) compared to the other group (group B) where the rim cutter was not used. This difference was statistically significant (p< 0.0001). Two cases in the non rim cutter group showed radioluciencies in Zone I. Similarly, with regard to the lateralisation of the COR, the implants in the rim cutter group were closer to the COR of the contralateral normal hip The cement mantle was found to be more concentric in the rim cutter group (in group A, more patients had the same width of cement mantle in all Zones) than the non rim cutter group. This difference between the two groups was statistically significant (p< 0.0001).

Conclusions: The introduction of the new “rim cutter” represents a progression in the technique for the preparation of the acetabulum in cemented hip arthroplasty. It indicates a further step, following the introduction of flanged sockets.

We describe two patients aged 16 and 25 years with osteogenesis imperfecta who sustained displaced fractures of the acetabulum following minor trauma. The femoral heads were deformed by impact against the acetabular margin and both cases underwent surgical reconstruction. The quality of the bone and soft tissues made the operations challenging. There were potential complications specific to osteogenesis imperfecta, including bleeding, the creation of secondary fracture lines and shredding of the soft-tissue. The cases provide useful guidelines for addressing these difficulties.

Aims: The objective of our study is to elucidate the chondrogenic potential of free autologous periosteal grafts in treating articular cartilage defects, especially in complicated cases where apart from the cartilage defect there are coexisting lesions. Methods: 60 young rabbits were randomly divided in 5 groups. A cartilage defect 0.5 ⋄ 0.5 was created in both knees of each rabbit and covered with free autologous periosteal graft. In the right knee an additional ligamentous lesion was created. Results: All the knees were amputated at one, two and three months postoperatively. Apart from the histological examination, the cartilage specimens were tested biomechanically. An indentation test was used using a Shore A sclerometer and the data were evaluated and compared. In the test group the produced fibrocartilage or hyaline-like cartilage, was mechanically inferior (hardness 50–70 GPa) comparing to the control knees group (98 GPa). The results were statistically evaluated (using O’Driscoll’s histological grading scale and Wilcoxon rank sum test). Conclusions: Autologous periosteal transplantation can be used in daily practise, as it is a method relatively easy to perform with low cost and without any contra-indications. Nevertheless, in cases of unstable knees the method has poor results and ligamentous repair is recommended first.