NAVIGATED SHORTER INCISION OR SMALLER IMPLANT IN KNEE ARTHRITIS?

Abstract

The Authors performed a matched paired study between 2 groups UKR or CA-TKR implanted with a mini-incision (MICA group) in the treatment of isolated medial compartment knee arthritis. The Authors hypothesized that UKR offers a real less invasive surgery with lower economical costs despite a worse limb/implant alignment. Furthermore at a minimum 40 months follow-up they hypothesized that this small implant guarantees still both better clinical score and patient satisfaction than in the MICA group.

Thirty two patients with isolated medial compartment knee arthritis who underwent to a medial UKR from February 2001 to September 2002 were included in the study (UKR group). In all 32 knees the arthritic change was graded according to the classification of Älback ¹. Arthritic change did not exceed grade IV in the medial compartment and grade II in the patello-femoral compartment. All patients had an asymptomatic patello-femoral joint. All patients had a varus deformity lower than 8° and a body mass index lower than 30. No patient had any clinical evidence of ACL laxity or flexion deformity and all had a preoperative range of motion of a least 110°. At a minimum follow-up of 48 months, every single patients in group A was matched with a patient who had undergone a computer assisted TKR performed with a less invasive approach (shorter than 12 cm) for an isolated medial compartment knee arthritis between August 1999 and September 2002 (MICA group) in our hospital. At latest follow-up the clinical outcome was evaluated using both the Knee Society Score and a dedicated UKR score developed by the Italian Orthopaedic UKR Users Group (GIUM). The HKA angle and the Frontal Tibial Component angle (FTC) were measured at latest follow up on long leg standing anterior-posterior radiographs and the mean values between the 2 surgeons assessments were used as final values. Furthermore during the hospital staying we registered in both the groups when each patient was standing comfortably in full weight-bearing according to a self- answered questionnaire and the data were compared. Statistical analysis of the results was performed using parametric test (Student’s t-test). A statistical comparison of the percentage of results for the GIUM score was performed using the Chi-square test. A statistically significant result was given a p≤ 0.05.

Both hospital stay and operative time were statistically longer obviously in MICA group. In the UKR group the mean surgical time was 51.5 minutes (range: 36–75) (p< 0.001) while in the MICA group was 108.8 minutes (range: 80–132) (p< 0.001). In the UKR group the patients remained in the hospital for a mean of 5.1 days (range: 3–7) and in the MICA group 8.2 days (range: 4–16). At the latest follow-up the mean Knee Society Score was 80.5 (range: 70–100) and 78.4 (range: 70–87) for group A and B respectively. No statistically significant difference was seen for the Knee Society score between the 2 groups (p=0.08). The mean Functional score was 83.5 (range: 73–100) for group A and 78.8 (range: 59–90) for group B. A statistically significant difference was seen for the Functional score with superior results for group A (p=0.02). A statistically significant difference was seen for the GIUM score with better results for group A (p=0.01). The mean GIUM score was 76 (range: 67–90) and 73.02 (mean: 65–85) for group A and B respectively. At latest follow up the mean HKA angle was 176.8° for group A (range: 174°–182°) and 179.3° for group B (range 177–182) (p< 0.001). The mean FTC angle was 86.9° (range: 84°–90°) and 89.4° (range: 87°–92°) for group A and B respectively (p< 0.001). All TKR implants were positioned within 4 degrees of a HKA angle of 180° and FTC angle of 90°.

At the latest follow-up (minimum 48 months) no statistically significant difference was seen in the postoperative Knee Society score for either group. However, significant differences were seen between the 2 groups in the functional results and in the GIUM score with better results in the UKR group. All the patients achieved a range of motion greater than 120° and could walk for longer distances. During the hospital staying in this group the patients reported a statistically significant earlier full weight-bearing. This was despite a significant less accurate limb alignment. In addition to inferior results for the computer assisted mini-invasive TKR group the costs of the procedure were obviously greater because of the expensive implants and technology along with statistically significant longer surgical times and hospital stay