Posterior-compartment osteophytes are commonly encountered during TKA. They can limit or prevent terminal extension by tenting the posterior capsule and can cause coronal plane imbalance due to tenting of adjacent capsulo-ligamentous structures. Osteophyte removal is a principle of TKA soft-tissue balancing [2]. Failure to remove an osteophyte may result in unnecessary soft-tissue releases or lead to additional bone resection. Posterior femoral osteophytes can be difficult to remove because they are hard to see, and surgeons may be concerned about passing a sharp instrument posteriorly, near the popliteal neurovascular structures. Surgeons generally remove them after resection of the distal, anterior, and posterior femur and proximal tibia. After these resections, the surgeon should have easier access to the posterior compartment. However, this technique requires the surgeon to determine the femoral component rotation before osteophyte removal. In our experience, determining the femoral component rotation before large (> 1 cm) posterior osteophytes are removed can result in coronal plane imbalance of both the flexion and extension gaps because of the remaining tenting effect of the retained posterior osteophytes. Therefore, we suggest that surgeons remove these osteophytes before the anterior and posterior femoral cuts are completed. Here, we describe our technique, which allows access to the posterior compartment before the final femoral component rotation is determined [1]. This early posterior osteophyte removal technique is applicable to measured resection, kinematic alignment, as well as our preferred gap balancing technique. Many patients with large posterior osteophytes also have advanced medial-compartment arthritis and a fixed-varus deformity (Fig. 1A-B). After knee exposure, the deep medial collateral ligament is released to the mid-coronal plane of the tibia. Additional soft-tissue releases should then be delayed until all femoral and tibial osteophytes are removed. We favor resection of the extension space (distal femur and proximal tibia) followed by removal of medial and lateral distal femoral and peripheral tibial osteophytes that might tent surrounding ligamentous structures.Fig. 1 A-B: (A) AP radiograph of right knee with fixed varus deformity and advanced arthritis is shown. (B) Lateral radiograph of right knee with large posterior femoral osteophyte, denoted by arrow is shown. (Published with permission from Douglas A. Dennis MD).A spacer block is inserted into the extension gap. Residual medial soft tissue tightness is typically encountered, and so at this point we remove any large posterior femoral osteophytes. The femoral component sizing guide then is applied to determine femoral component size. With the knee flexed 90°, a laminar spreader is inserted into the lateral flexion gap and tensioned. A retractor is placed medially to protect the medial collateral ligament (Fig. 2). A 4-mm resection of the posterior aspect of the medial femoral condyle is performed with an oscillating saw, providing access to the posterior compartment (Fig. 3). The interface between osteophyte and native femur is then visualized (Fig 4). A curved osteotome is used to divide the osteophyte at that interface (Fig 5). During this maneuver, it is common to observe some degree of opening of the flexion gap since the tenting effect of the posterior femoral osteophyte on the posterior capsule and posterior oblique ligament has been eliminated. The posterior femoral osteophyte is then removed with a rongeur (Fig. 6). While this technique has been most commonly used to remove large posteromedial femoral osteophytes in knees with varus deformity, the technique is applicable and has been utilized in knees with valgus deformity and large posterolateral femoral osteophytes as well.Fig. 2: Intraoperative photo shows a planned posterior preliminary resection, marked in ink on the femur, and denoted by the arrow. A retractor is protecting the medial collateral ligament. (Published with permission from Douglas A. Dennis MD).Fig. 3: An oscillating saw used to perform preliminary resection provides access to the posterior compartment of the knee. (Published with permission from Douglas A. Dennis MD).Fig. 4: A demonstration of the interface of normal condyle of the femur and the posterior osteophyte is shown, indicated by the arrow. (Published with permission from Douglas A. Dennis MD).Fig. 5: A curved osteotome divides the posterior osteophyte from the normal bone of the posterior condyle. (Published with permission from Douglas A. Dennis MD).Fig. 6: A pituitary rongeur extracts the resected posterior osteophyte. (Published with permission from Douglas A. Dennis MD).Extension gap tension and balance then are assessed. If imbalance persists, additional medial soft-tissue releases are performed until the gap is balanced. The AP femoral cutting block is then applied using the surgeon’s preferred method to obtain a rectangular flexion gap (measured resection guide or flexion gap tensioning). The remaining steps of the TKA are then completed in routine fashion. Large posterior femoral osteophytes contribute to soft-tissue imbalance, and we believe benefit from early removal before extensive soft tissue releasing is performed and femoral component rotation is determined.
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Mar 13, 2019
Derrick A Foge + 4
Open Access