Introduction: The use of the Oxford Phase 3 unicompartmental knee arthroplasty (UKA) in the treatment of anteromedial osteoarthritis of the knee in elderly patients is controversial. The aim of this study was to analyse the performance of patients 75 years of age or older after surgery with the Oxford Phase 3 prosthesis by a minimally invasive technique.

Material and methods: Between January 1999 and September 2004, 128 Oxford Phase 3 prostheses were implanted by a single surgeon. Patients with a minimal follow up (FU) of one year were divided in two groups depending on age. (Group A less than 75 years, group B 75 years or more.) Loss to FU was documented. The pre and postoperative clinical outcome of the patient with the new implant was objectively evaluated by a visual analog pain and satisfaction score, the WOMAC Score, Oxford score, the Knee Society knee score and Knee Society function score. The range of motion (ROM) was documented.

Results: Fourty-five patients were under the age of 75 (group A). Thirty patients were 75 or older (group B). In the second group 4 patients were lost to FU: two deceased and two due to severe illness. Mean age (range) in the first and second group was 67 (47–74 yrs) and 79 (76–87) years respectively. Both groups had a mean FU time of 29 months. In the preoperative scores there was a significant difference in the WOMAC function score (49.7 A vs 42.4 B), Knee Society knee score (51.2 A vs 45.5 B) and the Knee Society function score (51.7 A vs 41.4 B).The pre-operative ROM was 120.1 (A) vs 122.7 (B) degrees. Comparing the postoperative scores a significant difference was found in the Knee Society knee score (89.1 A vs 78.0 B) and in the WOMAC function score (77.8 A vs 74.0 B). The Oxford score and the postoperative VAS for pain and satisfaction were slightly in favour for the younger group, but did not differ significantly. The postoperative ROM was 126 degrees in both groups.

Conclusions: This study shows that in both groups the scores are good to excellent but slightly in favour for the younger group of patients operated for anteromedial osteoarthritis using a minimally invasive approach. Patients’ satisfaction is high in both groups. The slight difference in scores may be due to the presence of comorbidity in the older patient. Although the follow up in this study is the shortterm we advocate the use of the Oxford Phase 3 prosthesis in the elderly patient. The minimally invasive technique will lead to better range of movement, a quicker recovery of the older patient with less risk of complications and will be in our opinion more cost-effective than total knee replacement.

Introduction: The introduction of the Oxford Phase 3 unicompartmental knee arthroplasty (UKA) by a minimally invasive technique has significantly changed the treatment of medial osteoarthritis of the knee joint. The purpose of this study was to analyse our early results and to evaluate the clinical importance of the learning curve of the procedure.

Material and methods: Patients who were operated between January 1999 and September 2003, were divided in two groups. Group A consists of 34 patients (35 prostheses) who were operated between January 1999 and December 2001 with a minimal follow-up (FU) time of 24 months. The second group (B) consists of 41 patients (44 prostheses) who had surgery between January 2002 and September 2003 with a FU of minimal 12 months. WOMAC score, Oxford score, Knee Society knee/function score, VAS for pain and satisfaction, radiographical alignment, operation time and complications were documented and compared between the two groups. A slight modification of the operation technique was applied in the second group.

Results: The Knee Society function score differed significantly in favour for group B (81.5 A vs 88.1 B; p< 0.05). The Knee Society knee score was: 86.7 (A) vs 89.7 (B). The postoperative VAS for pain and satisfaction were slightly in favour for the second group. The Oxford and WOMAC score did not differ significantly. The ROM was 125.1 (A) vs 126.7 (B) degrees. The operation time was 84 (A) vs 64 (B) minutes. The radiographical tibio-femoral alignment was 6.1 (A) vs 6.4 (B) valgus. Optimal radiographical positioning of the three components was 51% (18/35;A) vs 80 % (35/44;B). Two complications were encountered only in the first group: dislocation of the meniscal bearing component, and lesion of the lateral meniscus. There were three patients with moderate pain complaints in group A and two in B.

Conclusions: This study shows that when an appropriate surgical technique is mastered from the very beginning, good to excellent clinical results can be achieved even in the learning curve period. The positioning of the prosthesis, as confirmed by radiographical study, after using our own modification of the surgical technique was improved.