Computer-assisted patellofemoral arthroplasty: a mechanism for optimizing rotation.

We reviewed the early outcome of 4 primary Avon patellofemoral arthroplasties performed by a single surgeon in a 1-year period. All operations were performed to treat symptomatic osteoarthritis, which had failed conservative management. All 4 procedures were performed with intraoperative computer navigation to enable correct alignment of the prosthesis. The patients were assessed clinically using the Oxford knee score and Crosby and Insall score. Radiologically, they were assessed using plain radiographs and computed tomography long leg and dynamic axial alignment views of the prosthesis. All patients had excellent early clinical and radiological results proving intraoperative navigation produces safe, reliable, and reproducible implant position in patellofemoral arthroplasty.

Are systemic emboli reduced in computer-assisted knee surgery?: A prospective, randomised, clinical trial.

We undertook a prospective, randomised study using a non-invasive transcranial Doppler device to evaluate cranial embolisation in computer-assisted navigated total knee arthroplasty (n = 14) and compared this with a standard conventional surgical technique using intramedullary alignment guides (n = 10). All patients were selected randomly without the knowledge of the patient, anaesthetists (before the onset of the procedure) and ward staff. The operations were performed by a single surgeon at one hospital using a uniform surgical approach, instrumentation, technique and release sequence. The only variable in the two groups of patients was the use of single tracker pins of the imageless navigation system in the tibia and femur of the navigated group and intramedullary femoral and tibial alignment jigs in the non-navigated group. Acetabular Doppler signals were obtained in 14 patients in the computer-assisted group and nine (90%) in the conventional group, in whom high-intensity signals were detected in seven computer-assisted patients (50%) and in all of the non-navigated patients. In the computer-assisted group no patient had more than two detectable emboli, with a mean of 0.64 (SD 0.74). In the non-navigated group the number of emboli ranged from one to 43 and six patients had more than two detectable emboli, with a mean of 10.7 (sd 13.5). The difference between the two groups was highly significant using the Wilcoxon non-parametric test (p = 0.0003).Our findings show that computer-assisted total knee arthroplasty, when compared with conventional jig-based surgery, significantly reduces systemic emboli as detected by transcranial Doppler ultrasonography.

Blood loss after total knee replacement: effects of computer-assisted surgery.

We carried out a prospective randomised study to evaluate the blood loss in 60 patients having a total knee arthroplasty and divided randomly into two equal groups, one having a computer-assisted procedure and the other a standard operation. The surgery was carried out by a single surgeon at one institution using a uniform approach. The only variable in the groups was the use of intramedullary femoral and tibial alignment jigs in the standard group and single tracker pins of the imageless navigation system in the tibia and femur in the navigated group. The mean drainage of blood was 1351 ml (715 to 2890; 95% confidence interval (CI) 1183 to 1518) in the computer-aided group and 1747 ml (1100 to 3030; CI 1581 to 1912) in the conventional group. This difference was statistically significant (p = 0.001). The mean calculated loss of haemoglobin was 36 g/dl in the navigated group versus 53 g/dl in the conventional group; this was significant at p < 0.00001. There was a highly significant reduction in blood drainage and the calculated Hb loss between the computer-assisted and the conventional techniques. This allows the ordering of less blood before the operation, reduces risks at transfusion and gives financial saving. Computer-assisted surgery may also be useful for patients in whom blood products are not acceptable.

Loose intra-articular body following anterior cruciate ligament reconstruction.

We report a case of intra-articular fracture of a bioabsorbable fixation device from the femoral tunnel in an anterior cruciate ligament reconstruction using a bone-tendon-bone graft. Thirteen months after successful reconstruction surgery, the patient experienced episodes of locking and medial joint pain. There was no history of trauma and no symptoms of instability or swelling. On revision arthroscopy, a fractured tip of a bioabsorbable RIGIDfix cross pin (Mitek, Westwood, MA) was identified in the medial compartment of the knee. There was a broad area of chondral erosion affecting the medial femoral condyle and a small defect to the medial tibial plateau where the loose body had been lodged. The bone-tendon-bone graft was intact without disruption. After arthroscopy, the patient was symptom free for 3 weeks but then developed further symptoms of locking. Magnetic resonance imaging showed another loose body within the knee. A repeat arthroscopy was performed 6 weeks after the earlier procedure and another piece of the polylactic acid RIGIDfix cross pin was removed, this time from the lateral gutter. This case raises concern about the potential for breakage and resultant loose body formation that may occur after bioabsorbable cross-pin fixation and, particularly, the associated chondral damage that can occur if early intervention is not conducted.

A new technique for reconstructing the medial patellofemoral ligament.

Many surgical techniques exist for treating patella instability. Over recent years, attention has focussed on reconstruction of the medial patellofemoral ligament (MPFL). We report a procedure involving a lateral release, distal realignment of the tibial tubercle and anatomic reconstruction of the MPFL using a graft composed of a redundant strip of medial retinacular tissue. Nineteen patients (twenty-one knees) with chronic patellofemoral instability who had failed conservative treatment underwent this procedure and were assessed clinically and radiologically at an average of 23 months post-operation. No patients were lost to follow-up. There was no recurrence of subluxation or dislocation. All achieved levels of activity comparable to or improved compared to pre-operative uninjured levels. This combined procedure incorporating a previously un-described method of reconstructing the MPFL gives superior results compared to previous studies. No graft donor site morbidity occurred and patient outcome scores, especially objective stability of the patella to lateral shift, were excellent.

Failure of Austin Moore hemiarthroplasty: total hip replacement as a treatment strategy.

Forty six patients who underwent conversion of their Austin Moore hemiarthroplasty to a total hip replacement were assessed clinically and radiologically. Forty patients requiring conversion had either groin or thigh pain. Operative findings showed acetabular cartilage degeneration and femoral loosening as the main pathological process causing their symptoms. Total hip replacement gave complete resolution of the symptoms in 41 patients. We propose early conversion to total joint arthroplasty in patients with painful hemiarthroplasties.