The highly accurate anteriolateral portal for injecting the knee

Abstract

Background: The extended knee lateral midpatellar portal for intraarticular injection of the knee is accurate but is not practical for all patients. We hypothesized that a modified anteriolateral portal where the synovial membrane of the medial femoral condyle is the target would be highly accurate and effective for intraarticular injection of the knee.

Methods: 83 subjects with non-effusive osteoarthritis of the knee were randomized to intraarticular injection using the modified anteriolateral bent knee versus the standard lateral midpatellar portal. After hydrodissection of the synovial membrane with lidocaine using a mechanical syringe (reciprocating procedure device), 80 mg of triamcinolone acetonide were injected into the knee with a 2.0-in (5.1-cm) 21-gauge needle. Baseline pain, procedural pain, and pain at outcome (2 weeks and 6 months) were determined with the 10 cm Visual Analogue Pain Score (VAS). The accuracy of needle placement was determined by sonographic imaging.

Results: The lateral midpatellar and anteriolateral portals resulted in equivalent clinical outcomes including procedural pain (VAS midpatellar: 4.6 ± 3.1 cm; anteriolateral: 4.8 ± 3.2 cm; p = 0.77), pain at outcome (VAS midpatellar: 2.6 ± 2.8 cm; anteriolateral: 1.7 ± 2.3 cm; p = 0.11), responders (midpatellar: 45%; anteriolateral: 56%; p = 0.33), duration of therapeutic effect (midpatellar: 3.9 ± 2.4 months; anteriolateral: 4.1 ± 2.2 months; p = 0.69), and time to next procedure (midpatellar: 7.3 ± 3.3 months; anteriolateral: 7.7 ± 3.7 months; p = 0.71). The anteriolateral portal was 97% accurate by real-time ultrasound imaging.

Conclusion: The modified anteriolateral bent knee portal is an effective, accurate, and equivalent alternative to the standard lateral midpatellar portal for intraarticular injection of the knee.

Trial registration: ClinicalTrials.gov: NCT00651625.

Figure 1

Palpation-Guided Anatomic Markers. Anatomic landmarks are first identified by palpation and marked with ink prior to the procedure for both palpation-guided procedures. VL (vastus lateralis), LF (lateral femoral condyle), LTP (lateral tibial plateau), PT (patellar tendon), P (patella), T (target for anteriolateral bent knee approach).

Figure 2

Introduction of the Needle from the Anteriolateral Portal. The reciprocating procedure device (RPD) control syringe is used with two hands to carefully introduce the needle and administer lidocaine. Depressing one plunger causes the RPD control syringe to aspirate and depressing the other causes the device to aspirate. If no fluid is obtained the needle is advanced to the medium femoral condyle.

Figure 3

Modified Anteriolateral Portal. With the modified anteriolateral portal and the knee in the bent position, the needle is directed from the anteriolateral portal, under the patellar tendon, to the synovial surfaces of the medial femoral condyle rather than the intercondylar notch.

Figure 4

Lateral Midpatellar Portal. With the lateral midpatellar portal and the knee is almost fully extended, the needle is directed from the lateral midpatellar position into the patellofemoral joint space.

Figure 5

Placement of Ultrasound Probe. After introduction of the needle, the ultrasound probe is placed over the anteriomedial portal so that the ultrasound beam is at right angles to the needle shaft optimizing visualization of the location of the needle tip engaged to the medial femoral condyle.

Figure 6

Sonographic Visualization of Needle Placement. The needle is advanced until the needle tip palpably engages the medial femoral condyle.

Figure 7

Sonographic Visualization of Direct Intraarticular Injection. After the needle tip is advanced until it palpably engages the medial femoral condyle, lidocaine is injected showing fluid movement into the intraarticular space and dilation of the intraarticular space. Here intraarticular movement of fluid is demonstrated by color Doppler at the needle tip with simultaneous dilation of the intraarticular space.