Introduction

Derotation osteotomies are commonly performed in paediatric orthopaedic and limb reconstruction practice. The purpose of this study was to determine whether the use of a digital inclinometer significantly improves the accuracy in attaining the desired correction.

60 out of total series of 643 metal-on-metal hip replacements, carried out over the last nine years, have so far required revision, 13 for peri-prosthetic fracture and 47 for extensive, symptomatic, peri-articular soft-tissue changes.

Dramatic corrosion of generally solidly fixed, cemented stems has been observed and is believed to have resulted in the release of high levels of cobalt chrome ions from the stem surface. The contribution of the metal-to-metal articulation is, as yet, unclear.

Not including the fracture cases, plain films have demonstrated little or no abnormality to account for patients’ progressive symptoms. MRI scanning, on the other hand, utilising a technique designed to minimise implant artefact, has correlated very closely with findings at the time of revision surgery.

The histological changes, typified by extensive lymphocytic infiltration and a severe vasculitis leading to, in some cases, extensive tissue necrosis are demonstrated and discussed.

The failure of any of the existing protective mechanisms or regulatory restrictions to identify and limit the exposure of large numbers of patients to unsatisfactory implants has again been demonstrated.

Introduction: Patellofemoral instability (PFI) is a disabling condition that occurs in adolescence. Recurrence after patellar dislocation has been reported in 2–50% of cases. This study aimed to compare the shape of the distal femur in PFI to a normal cohort.

Method: 108 CT scans from 54 subjects with PFI were compared to 197 CT scans from 102 normal subjects. Outlines of the trochlear groove and lateral condyle were extracted from CT scans using Interactive Data Language version 5.0 image manipulation software. The shapes were aligned using a modified Procrustes analysis and interpolation performed with a basic cubic spline. A statistical method from the field of functional data analysis was used to quantify shape. A discriminant analysis was then used to provide a tool for deciding which patients had abnormal grooves thus improving patient selection for trochleoplasty.

Results: Mathematical quantification showed a significant difference at the 0.001 level using an independent t-test between the normal and PFI groups for the shape of the trochlear groove with PFI knees having a more complex shape than normal. The second largest source of variation is in the position of the trochlear groove minimum with respect to the coronal plane together with variation in the shape of the medial condyle. The trochlear groove is situated more medially, with a shallower medial condyle, in PFI. In contrast the trochlear groove is situated more laterally, with a more prominent medial condyle in normal knees. Analysis of shape of the lateral condyle showed that in PFI, it is shorter and broader.

Conclusion: Principal components analysis can be used to quantify the variation in shape of the distal femur and allow a discriminant function analysis to be performed comparing PFI knees to normal knees. This quantification of shape can be applied to diagnosis of instability, operative planning for trochleoplasty and implant design.

Introduction and Aims: Dysplasia of the femoral sulcus is one component that may be present in patients presenting with patellar instability. Rarely the dysplasia is so severe that a dome rather than groove is present. Dejour has reported an operation that deepens the groove, unlike the Albee which elevates it. This study reports the development of a modification of the Dejour trochleoplasty reporting the clinical and radiological results.

Method: A consecutive case series of the first 15 patients (17 knees) who underwent a trochleoplasty with a minimum one-year follow-up. There were 11 females and four males with an age range from 15 to 47 years old. Nine patients had had previous operations. The pre-operative length of symptoms ranged from one to 30 years. The patellar instability was managed operatively using the Dejour protocol measuring the patellar height, boss height, tibial tubercle-trochlear groove distance and patellar tilt angle. The Kujala score was used for functional assessment and a subjective assessment was also made. CT scans as well as plain films were used for radiological assessment. The operative technique changed in the light of experience from metallic to absorbable screws as the former abraded the patella.

Results: The boss height was reduced from an average of 7.5mm to 1mm (normal 0mm). Tracking became normal in 11 knees and had a slight J-shape in six. Seven knees had a mild residual apprehension. Five patients were very satisfied, eight were satisfied, and two were disappointed. The Kujala score improved from an average of 48 to 73 out of 100. Three patients returned to full sports. Eight patients required further operations apart from the removal of metallic screws in 10 knees. Five of these were arthrolysis for stiffness at about six weeks post-operatively. As a result, patients were placed on a continuous passive motion machine for three to four days to avoid this. One patient went on to have autologous chondrocyte implantation for a defect on the lateral femoral condyle involving the tibial surface. This was after a new injury following a return to sports and not in the area affected by the trochleoplasty.

Conclusion: Trochleoplasty for severe dysplasia of the femoral sulcus is a developing procedure. It requires careful attention to detail. For a rare condition the results have been gratifying with an acceptable level of complications. It is not recommended that this procedure be performed by general orthopaedic surgeons.

The positioning of components in knee replacement is related to outcome and for this reason a study has been conducted to compare the exact position of the tibial and femoral components in total knee arthroplasty with the placement as judged by the surgeon at the time of operation.

Operating surgeons of a range of grades completed a pro-forma immediately after operating on 25 patients having total knee replacement. Patients were entered into the study by consent providing that they had osteoarthritis and this was their first ever lower limb joint replacement. The form detailed where the surgeon considered he had placed the femoral component in the coronal plane and in terms of rotation upon the femur. They were asked to state what lines or angles of reference they had used and whether they had used intra or extra medullary jigs. Likewise for the tibia, implant position was detailed for coronal, sagittal and transverse planes. The proforma stated the grade of operating surgeon but were otherwise kept anonymous.

All study patients had pre and postoperative CT scans. These involved an AP scannogram and transverse sections, according to a protocol, through the femoral neck, femoral condyles, tibial plateau and ankle. By comparing bony landmarks seen on the pre-operative CT scans with lines of reference from the components post-operatively the exact position of the implant was determined in the transverse and coronal planes. For the sagittal plane (slope) the standard lateral X-ray was used.

For the femur all operations were carried out using intra-medullary jigs. For the femoral component the difference was not significant between the measured position and the surgeons estimate in any plane (p=0.937 for coronal and p=0.432 for transverse). The measured position of the component was not related to the grade of the operating surgeon nor to the axis nor technique of reference used.

For the tibial component, coronal alignment was significantly different (p=0.001) with the measured position being in more varus than was estimated. The range of transverse placement was from 4° of external rotation to 35° of internal rotation of the tibial prosthesis with reference to the tibial tubercle centre. This was significantly different to that estimated by the surgeon (p< 0.001). Estimation of slope in the sagittal plane was good. None of these differences were related to operator grade. For 15 of the TKR’s the tibail component was aligned using intra-medullary techniques. This was related to the accuracy of positioning of the prosthesis with significantly better estimation compared to those in which extra-medulary jigs had been used (p=0.002 for the transverse plane and p=0.065 for the coronal plane).

This study has demonstarted that surgeons are able to accurately judge the position of insertion of the femoral component in total knee replacement. Surgeons are poor at estimating the position of the tibial component in the transverse and coronal planes but better in the sagittal plane. Due to the difficulty in its assessment rotational alignment has been ignored in arthroplasty but as with alignment in the other planes it is likely to have a bearing on outcome. Improved techniques to help us judge placement of knee components are needed.