Introduction This prospective outcome study presents the results and complications of 41 lateral unicompartmental knee joint replacements.

Methods One surgeon operated on all the patients in this series. The surgery was performed through minimally invasive techniques wtih the patients being day-stay or overnight stay patients. Assessment was made using SF-36 and WOMAC questionnaires, physical examination, x-ray pre-operatively and at six monthly intervals. Kaplan-Meier survival analysis was carried out.

Results Forty-one knees (39 patients) underwent surgery. There were 15 males (average age 64 years) and 26 females (average age 68 years). Mean follow-up time was 3.2 years (max 4.6 years). Of these four were Repicci inlay components, 10 were Repicci onlay components and 28 were Oxford mobile bearing implants. Three patients required reoperation, all having mobile bearings in place. One required revision to total knee replacement for progression of arthritis in the medial compartment, and two for bearing dislocation. The operation consisted of a change of bearing to a thicker one. One of these patients had a further complication, a deep infection which was treated successfully with arthroscopic debridement and antibiotics. Another of the mobile bearing patients had a DVT. WOMAC and SF36 show a reduction in pain and stiffness, and an increase in physical function and quality of life. Kaplan-Meier analysis shows 100% survival of the fixed implants but 96% in the mobile bearing group. However 11% of the mobile bearing group required reoperation.

Conclusions Lateral compartment replacement is a technically demanding procedure. This study looks at the early results, and does not examine long-term wear. A significant difference in the complication rates for the different type of implant is noted, with the mobile bearing having a higher reoperation rate.

In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source.

Introduction: Bone fragility is a result of the reduction in bone mineral density and mass. This reduction directly reduces the effectiveness of trabecular cross bracing. The problem of femoral neck fractures after hip resurfacing surgery is directly related to the mechanical load on the osteoporotic bone.

Aim: To determine any correlation between the degree of osteoporous and subsequent femoral neck fractures.

Methods: A comparison was made between both femoral necks in the same patient, to determine the degree of osteoporosis prior to surgery. These results were then compared with subsequent changes in osteoporosis 12 months post-operatively.

Bone mineral density values, were used to compare the non-operative femoral neck to the operative femoral neck before surgery. These values were then used as a predictive risk of subsequent femoral neck fracture in this patient group. Bone mineral density assessments were repeated 12 months after the surgery to compare the subsequent changes in the osteoporotic values. The bone mineral density evaluations were carried out on one hundred patients, both male and female between the ages of 28 and 87 years. The criterion for entry into this group was a bone mineral density value of no lower than 1.5 standard deviation points below the young reference value.

Results: We found an improvement in the bone mineral density values for each patient, therefore reducing the risks of subsequent femoral neck fracture.