Abstract
Introduction: There is little dispute that flexion and extension spaces should be rectangular and equal in a knee replacement and that rotation of the femoral component has a bearing on function and outcome. However, there is dispute over what is the ‘correct’ rotation and how best to achieve it. Transepicondylar line, computer navigation, 3 degrees external rotation have all been tried with a similar lack of reliability (Siston et al, JBJS Am, 2005 Oct; 87(10):2276–80) Insall and Scuderi recommended placing a tensor in the knee in flexion and rotating the femoral cutting block so that its posterior edge is parallel to the top of the tibia (Scuderi et al, Orthop Clinc. North. America, 20:70–78, 1989)
We feel the Equiflex instrumentation designed by Mr Lennox will reliably achieve Insall and Scuderi’s recommendation and reduce the incidence of lateral retinacular release
Purpose of Study: To evaluate early clinical results and lateral retinacular release rates using Equiflex instrumentation to do TKR
Method: We evaluated 209 consecutive knees done with this technique at Basildon from 4 April 05 – 19 September 06. Pre and postop American Knee Society and Oxford scores, deformity, ROM were recorded for the 152 cases with 6 week follow-up. Lateral retinacular release rates and complications are presented for the entire cohort of 209 cases.
Results: Average inpatient stay −4.9 days (20% discharged in −3 days) if we exclude complications. There were 31 Valgus knees, 178 varus knees with an average alignment of 5.95 (23 degree varus − 25 degree valgus). 38 uncemented knees.
At 6 weeks, Knee score improved from 34.5 to 78.5, function score improved from 47.5 to 49.8, oxford score improved from 43.4 to 30.06. Average preop flexion was 105 degrees (65–130) and average postop flexion was 98 (40–130)
We could correct alignment and achieve our technical goals in 99% of cases
A lateral retinacular release was required in only 5 out 31 valgus knees (16%) and 0 out of 178 varus knees (a total lateral release rate of 2.4%)
Complications: Wound or ipsilateral skin problems – 10 (4.7%) all of which settled rapidly with antibiotics. Thromboembolic phenomena – 13 cases (6.2%) – 9DVTs, 5 PE. MUA – 3 (2.3%). Hairline crack of tibial cortex in soft porotic bone– 3 (1.4 %). MI – 2 (1 postop, 1 at 4 weeks). CVA – 4 (1 postop, 1 at 6 weeks). Confusion – 2. GI bleed -2 . Bleeding PR, Ca Rectum -1.
Discussion: Perioperative complications probably under-reported in studies with> 1 year follow up. Callahan et al in their metaanalysis of literature from 1966–1992 did not include delayed wound healing, wound drainage, haematoma, urinary retention etc. They found a weighted mean complication rate of 18.1 % with a mortality per year of followup of 1.5%. Studies which have specifically looked at complications have reported an average of 3.9% superficial infections, 1.7% deep infections, 6.5% DVTs and 2.1% peripheral nerve damage (9).
Our complication rates were well within published data and we could correct alignment and achieve our technical goals in 99% of cases. We required to do a lateral retinacular release only in 5 valgus knees with subluxed patellae and contracted lateral structures for an overall release rate of 2.4%.
Conclusions:
-
This is a safe, effective and reproducible procedure with complications comparable to published data
-
The equiflex instrumentation does help in equalising the flexion-extension gaps, improves patellar tracking and reduces the incidence of lateral retinacular release
-
Design modification to include a calibrated quantifi-able tensioner may be helpful
-
Further follow up of the same cohort would be desirable to get medium and long term results.
Correspondence should be addressed to: Tim Wilton, BASK, c/o BOA, The Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE.
