Abstract

The knee is one of the most commonly affected joints in osteoarthritis. Unicompartmental knee replacement (UKA) was developed to address patients with this disease in only one compartment. The conventional knee arthroplasty jigs, while usually being accurate, may result in the prosthesis being inserted in an undesired alignment which may lead to poor post-operative outcomes. Common modes of failure in UKA include edge loading due to incorrect sizing or positioning, development of disease in the other compartment due to over-stuffing or over-correction and early loosening or stress fractures due to inaccurate bone cuts.

Computer navigation and robotically assisted unicompartmental knee replacement were introduced in order to improve the surgical accuracy of both the femoral and tibial bone cuts. The aim of this study was to assess accuracy and reliability of robotic assisted, unicondylar knee surgery in producing reported bony alignment.

Two hundred and twenty consecutive patients with a mean age of 64 + 11 years who underwent successful medial robotic assisted unicondylar knee surgery performed by two senior total joint arthroplasty surgeons were identified retrospectively. The mean body mass index of the cohort was 33.5 + 8 kg/m² with a minimum follow-up of 6 months (range: 6–18 months). Femoral and tibial sagittal and coronal alignments as well as the posterior slope of the tibial component were measured in the post-operative radiographs. These measurements were compared with the equivalent measurements collected during intra-operative period by the navigation to study the reliability and accuracy of femoral and tibial cuts. Radiographic evaluation was independently conducted by two observers.

There was an average difference of 2.2 to 3.6 degrees between the intra-operatively planned and post-operative radiological equivalent measurements. For the femur, mean varus/valgus angulation was 2.8 + 2.5 degrees with 83% of those measured within 5% of planned. For the tibia mean varus/valgus angulation was 2.4 + 1.9 degrees with 93% within 5% of planned resection. There was minimal inter-observer variability between radiographic measurements. There were no infections in the evaluated group at the time of radiographic examination.

Alignment for unicondylar knee arthroplasty is important for implant survival and is a more difficult procedure to instrument as it is a minimally invasive surgery. Assuming appropriate planning, robotically assisted surgery in unicondylar knee replacement will result in reliably accurate positioning of component and reduce early component failures caused by malpositioning. A mismatch between pre-planning and post-operative radiography is often caused by poor cementing technique of the prosthesis rather than incorrect bony cuts. Addressing these factors can lead to greater success and improved outcomes for patients.

The aim of this study was to assess the increase in the anterior diameter of the knee and the impact of this increase on the range of motion and function of the knee.

Twenty-eight patients (34 knees) who underwent Patello-femoral replacement with FPV (Wright Medical) prosthesis between 2005 and 2009 who were identified retrospectively and analyzed using chart and radiological review. Oxford and AKSS knee-scores were gathered prospectively pre-operative and at follow-up.

Trochlear height was measured using lateral radiograph. Trochlear height was compared pre and postoperatively. Patellar height was also measured in preoperative and postoperative skyline view and was compared. The range of movement at six weeks and the Oxford and American knee society knee scores at six months postoperatively were noted. Association between increased anterior height and improved range of motion was studied.

All but three-knees regained full knee extension. Postoperative mean range of flexion of the knee joint was 116 degrees. The mean Oxford knee and the mean American Knee Society Knee Scores significantly improved post-operatively

The trochlear height was increased by 4mms. Patellar height was also increased by 3 mms resulting in average total increase of 7 mms in the anterior-posterior diameter of the knee. We found no relationship between range of motion of the knee and the increase in the anterior-posterior diameter. We found a negative correlation between increase in the antero-posterior and preoperative trochlear and patellar height.

We conclude that FPV Patello-femoral replacement results in correct anatomical reconstruction of the trochlear height rather than ‘overstuffing’ of the patellofemoral joint which can lead to stiffness and failure of resolution of pain post-operatively. This should in turn result in durable improvements in pain and function.

The conventional Knee arthroplasty jigs, while being usually accurate, often result in prostheses being inserted in an undesired alignment resulting in poor postoperative outcome. This is especially true about unicompartmental knee replacement. Computer navigation and roboticaly assisted unicompartmental knee replacement were introduced in order to improve surgical accuracy of the femoral and tibial bone cuts.

The aim of this study was to assess accuracy and reliability of robotic assisted, unicondylar knee surgery (Makoplasty) in producing reported bony alignment. Two hundred and twenty consecutive patients who underwent medial robotic assisted unicondylar knee surgery (Makoplasty) performed by two surgeons (RJ & GP) were retrospectively identified and included in the study. Femoral and tibial sagittal and coronal alignments and posterior slope of the tibial component were measured in the post-operative radiographs. These measurements were compared with the equivalent measurements collected during intra-operative period by the navigation to study the reliability and accuracy of femoral and tibial cuts.

Recently in the literature the indications of unicompartmental knee arthroplasty have been extended by the inclusion of patients with arthritis which is predominantly but not exclusively effecting the medial compartment. The aim of this study is to evaluate the outcome of MAKO unicondylar replacement in the treatment of knee osteoarthritis after the initial surgical insult is worn off to evaluate the impact of residual patellofemoral and lateral osteoarthritis on the outcome of medial unicompartmental knee replacement.

135 patients who underwent uncomplicated 144 MAKO medial unicondylar replacements for knee arthritis were identified and studied. Original radiographs were used to classify severity of patellofemoral and lateral compartmental osteoarthritis in these patients. Severity of patellofemoral and lateral compartmental osteoarthritis was analyzed against Oxford and Knee Society (AKSS) scores and amount of ipsilateral residual knee symptoms at 6 months post-operative period.

Pre-operative Oxford and Knee Society scores, and other comorbidities and long term disability were studied as confounding variables.

We found significant improvement in symptoms and scores in spite of other compartment disease. Poorer outcome was seen in association with comorbidities and long term disability but not when radiographic signs of arthritis in the other compartments were present. Six patients required revision of which three had (lateral facet) patellofemoral disease in the original x-rays.

In conclusion there is no direct relationship between postoperative symptoms and poor outcome and radiographic disease in the other compartments. However when symptoms are severe enough to necessitate revision this is due to patellofemoral and not lateral compartment disease.