Np Walton

Revision of medial Oxford unicompartmental knee replacement to a total knee replacement: similar to a primary?

Unicompartmental knee replacement (UKR) is an option for the treatment of isolated medial compartment osteoarthritis. A commonly perceived potential advantage is that revision of a UKR is straightforward. The purpose of this study was to determine the early outcomes and the level of complexity of revisions of Oxford UKRs performed at our hospital. A retrospective review of a prospective database of all phase III Oxford UKRs was undertaken. This identified 89 Oxford UKRs which were revised at our institution between 2002 and 2008. The median time from the primary procedure to revision was 19 months (interquartile range 2-73 months). Nine were revised to another UKR. Eighty were revised to a total knee replacement (TKR). Fifty-three were revised with primary TKR components. Twenty-seven were revised using stems and/or augments. The median overall tibial component thickness (including augments) was 15 mm. Forty-five knees had an overall tibial component thickness greater than 15 mm. A primary Oxford UKR bearing thickness of greater than 6mm was associated with an increased likelihood of requiring revision components. On the basis of this review, tibial bone defects were commonly encountered when revising UKRs. Reconstruction with either an augment and a stem, or thick polyethylene component was often required. We recommend that the potential complexity of revision for UKR failure should be borne in mind when considering a primary Oxford UKR.

Assessment of radiolucent lines around the Oxford unicompartmental knee replacement: SENSITIVITY AND SPECIFICITY FOR LOOSENING

The Oxford unicompartmental knee replacement gives good results in patients with symptomatic osteoarthritis of the medial compartment. Previous studies have suggested that the presence of radiolucent lines (RLLs) does not reflect a poor outcome in such patients. However, the reliability and validity of this assessment have not been determined. Our aim was to assess the intra- and interobserver reliability and the sensitivity and specificity of the assessment of RLLs around both tibial and femoral components using standard radiographs. Two reviewers assessed the radiographs of 45 patients who had loosening of the tibial or femoral component confirmed at revision surgery and compared them with those of a series of 45 asymptomatic patients matched for age and gender. The results suggested that, using standard radiographs, tibial RLLs were 63.6% sensitive and 94.4% specific and femoral RLLs 63.9% sensitive and 72.7% specific for loosening. Overall intra- and interobserver reliability was highly variable, but zonal analysis showed that lucency at the tip of the femoral peg was significantly associated with loosening of the femoral component. Fluoroscopically guided radiographs may improve the zonal reliability of the assessment of RLLs, but further independent and comparative studies are required. In the meantime, the innocence of the physiological RLLs detected by standard radiographs should be viewed with caution.

Ipsilateral tibial shaft fracture and distal tibial triplane fracture with an intact fibula: a case report

We present a case of an ipsilateral tibial shaft fracture and a distal tibial triplane fracture with an intact fibula in a 14-year-old boy. Computed tomography revealed the distal tibial triplane fracture with a 2.6-mm displaced Tillaux fragment and a posterior malleolar shear fragment. Open reduction and internal fixation was performed to optimise healing and outcome. This is a rare injury, for which a high index of suspicion is needed for diagnosis. Missing the intra-articular distal tibial triplane fracture could result in a disabling angular deformity (mostly varus) or limb-length discrepancy secondary to premature partial closure of the distal physis.

A subtle intra-operative complication of the IMHS that may go unnoticed

We present two cases with intra-operative complications during the placement of intra-medullary hip screw (IMHS). In both occasions, the implant accidentally breached the anterior cortex of the distal femur. Lateral view with image intensifier confirmed the perforation. This intra-operative complication has not been reported before. It is unclear how often this occurs and how often we miss these subtle complications with potentially disastrous consequences. In the event that it does occur, it is arguable whether any intra-operative or post-operative precautions should be taken. Intra-operative complications with particular reference to femoral fractures is a risk, which when occurring could drastically change the course of management. Although this can be subtle, in general, this will be easily visible on image intensifier. On the other hand, femoral shaft perforations can be a lot more subtle if they are noticed at all. If this complication is not noted and the management does not take this into account, a consequential fracture (eg. Supracondylar or peri-prosthetic) and further complications can result. Possible causes for femoral cortex breaching can be numerous. It is questionable if the breaching is noted whether it should be protected with further internal fixation, casting support or altering the weight-bearing state post-operatively. In one of our cases, the surgeon used extra-medullary device (LISS plate) and for the other, the surgeon managed this conservatively. Different surgeon different management but similar good outcome.