Treatment of Acetabular Fractures in Older Patients

Fig. 7.1

AP view of the pelvis demonstrating corridors for anterior column, posterior column, LC-2, and “magic” screws

Anterior Column Screw

The screw is placed in a bony corridor that runs from the parasymphyseal bone of the pubis medially to the supraacetabular bone of the ilium laterally. The osteology varies by patient and the screw can be placed in an antegrade (lateral to medial) or retrograde (medial to lateral) fashion, although an antegrade passage is usually chosen for acetabular injuries. Antegrade screws can be placed in a supine, lateral, or prone position [25–27]. Retrograde screws require supine positioning [26]. Protrusio of the hip joint may narrow the pathway (Fig. 7.2a) or preclude screw placement altogether (Fig. 7.2b). The corridor typically narrows at two locations: the supraacetabular region and the directly superior to the obturator ring (Fig. 7.3). The outer, or thread, diameter of the screw chosen should be based upon the diameter and collinearity of these constriction points (Fig. 7.4a, b). Fluoroscopic imaging with obturator outlet and inlet views is used to safely place a screw above the acetabulum and within the superior ramus medially (Fig. 7.5a, b; obturator outlet with an antegrade screw and inlet with an antegrade screw).

../images/395168_1_En_7_Chapter/395168_1_En_7_Fig2_HTML.jpg — Fig. 7.2

(a) Protrusion of the native hip joint narrows the anterior column corridor and prevents placement of an antegrade screw above the obturator ring into the parasymphyseal bone of the pubic ramus. (b) A narrow canal of the superior ramus with diameter less than 3.5 mm on coronal computed tomography imaging precludes use of an anterior column screw

../images/395168_1_En_7_Chapter/395168_1_En_7_Fig3_HTML.jpg — Fig. 7.3

Obturator oblique view of the hip showing the constriction points of the anterior column screw pathway

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(a) Obturator oblique view permits 4.5 mm diameter or less screw. (b) Obturator oblique view permits a fully threaded 7.3 mm screw

../images/395168_1_En_7_Chapter/395168_1_En_7_Fig5_HTML.jpg — Fig. 7.5

(a) Obturator outlet and (b) inlet views after antegrade anterior column screw placement

Posterior Column Screw

The screw is placed in the bony corridor between the pelvic brim and ischial tuberosity posterior to the acetabulum and anterior to the greater and lesser sciatic notches. Screws may be placed in antegrade or retrograde fashion. Antegrade placement is accomplished in a supine positioning and requires limited open approach with a portion of the lateral window of the ilioinguinal approach. The hip and knee are gently flexed with a triangle or surgical bump to relax the iliopsoas and femoral nerve. The starting point is immediately lateral to the pelvic brim and approximately one to 4 cm anterior to the sacroiliac joint (Fig. 7.6). An antegrade screw usually ends just below the ischial spine near the lesser sciatic notch as the chest wall limits a more anterior trajectory to reach the ischial tuberosity (Fig. 7.7a, b).

../images/395168_1_En_7_Chapter/395168_1_En_7_Fig6_HTML.jpg — Fig. 7.6

3D surfaced rendered iliac oblique view demonstrating the area for starting point (highlighted in blue) of an antegrade posterior column screw

../images/395168_1_En_7_Chapter/395168_1_En_7_Fig7_HTML.png — Fig. 7.7

(a) Clinical photograph of antegrade posterior column screw placement through the lateral window of the ilioinguinal approach. (b) Iliac oblique view showing an antegrade posterior column guidewire terminating just below the ischial spine near the lesser sciatic notch

Retrograde screws can be placed with the patient in a supine or prone position. Regardless of positioning, great care must be taken to maintain sterility due to the proximity of the perineum. Supine positioning requires an assistant to flex the hip and knee (Fig. 7.8a) and the patient should be placed on a midline sacral bump prior to the prep and drape. The starting point on the ischium risks damage to the inferior cluneal nerves and is remote from the posterior cutaneous nerve of the thigh and the sciatic nerve [28]. Fluoroscopic imaging with iliac oblique, anteroposterior, and obturator oblique views is used to place the screw. Iliac oblique view confirms the screw is posterior the acetabulum and anterior to the greater and lesser sciatic notches (Fig. 7.8b). The screw should be immediately lateral to the ilioischial line with an anteroposterior view (Fig. 7.8c). A lateral sacral view is particularly helpful with retrograde screw placement to evaluate the proximal endpoint of the screw and prevent protrusion into the iliac fossa and iliacus muscle.

../images/395168_1_En_7_Chapter/395168_1_En_7_Fig8_HTML.png — Fig. 7.8

(a) An assistant flexes the hip and knee to permit supine placement of a retrograde posterior column screw. (b) Iliac oblique and (c) anteroposterior fluoroscopic views with a posterior column screw in place

The LC-2 Screw

This screw is placed in the supraacetabular bone between the anterior inferior iliac spine (AIIS) and the posterior inferior iliac spine (PIIS). The bony corridor is familiar to surgeons using anterior half pins for external fixator placement. A screw may be placed from anterior to posterior or posterior to anterior, although the former is most commonly used for acetabular fracture fixation. The lateral femoral cutaneous nerve is at risk with anterior to posterior placement [29]. Skin incision is localized using an obturator outlet view, where the “teardrop” is identified (Fig. 7.9a), which looks down the bony corridor between the AIIS and PIIS. Iliac oblique view (Fig. 7.9b) ensures the screw starts above the acetabulum near the AIIS and passes cranial to the greater sciatic notch. An obturator inlet (Fig. 7.9c) view shows placement between the inner and outer tables of the ilium and lateral to the sacroiliac joint.

../images/395168_1_En_7_Chapter/395168_1_En_7_Fig9_HTML.png — Fig. 7.9

(a) Obturator outlet view demonstrating the “teardrop,” which represents the column of bone from the AIIS to PIIS. (b) Iliac oblique and (c) obturator inlet views after placement of an LC-2 screw from anterior to posterior

The “Magic” Screw

This screw is placed from the lateral ilium to the quadrilateral plate cranial and/or posterior to the acetabulum and is used in an attempt to maintain reduction of a medialized caudal segment . Branches of the superior and inferior gluteal neurovascular bundles are at risk during placement of the screws. The further anterior to the greater sciatic notch with the starting point, the lesser the risk to the main trunks of the vessels and nerves. Anteroposterior and Judet views (Fig. 7.10a–c) are used to ensure extraarticular placement.

../images/395168_1_En_7_Chapter/395168_1_En_7_Fig10_HTML.jpg — Fig. 7.10

(a) AP, (b) iliac oblique, and (c) obturator oblique views after “magic” screw placement (highlighted in yellow)

Reduction Techniques

Reduction techniques can be generally divided into indirect maneuvers and direct techniques applied through limited incision. Detailed knowledge of the soft tissue anatomy about the pelvis is mandatory prior to embarking on percutaneous or limited open treatment of acetabular fractures. A portion of the lateral window of the ilioinguinal approach is frequently used for direct techniques with clamp applications [14]. Specialized instruments have been developed to assist with these techniques (Fig. 7.11) and are now commercially available (Smith and Nephew, Memphis, TN, USA). The collinear clamp (DePuy Synthes, Paoli, PA, USA) (Fig. 7.11) may also be placed using a limited opening of the lateral window. One of the benefits of larger open approaches is the ability to directly see and clean the fracture line(s) and remove entrapped soft tissues and fracture hematoma. For this reason, prompt surgery shortly after the time of injury is recommended if percutaneous and limited open technique is chosen. A long delay from injury, when hematoma is organized, will typically require open approaches. Regardless of the timing of operation, the surgeon must be prepared to convert to more invasive open approach(es) if appropriate reduction cannot be achieved with minimally invasive techniques.

../images/395168_1_En_7_Chapter/395168_1_En_7_Fig11_HTML.jpg — Fig. 7.11

Photograph of (a) “rib tickler,” (b) collinear clamp, and modified offset (Reinert) clamp with (c) paddle or ball-spike (d) for quadrilateral surface

The sequencing of fixation should be similar to sequencing with traditional open approaches. For associated both column injuries, the dome is first reduced and fixed to the intact ilium. The remaining fracture fragments are then reduced and stabilized to the dome, as they would be in associated fracture patterns where the dome has not been separated from the intact ilium. With osteochondral impaction of the dome, which is common, reduction is performed after the cranial femoral head has been located under the intact lateral dome. Below specific reduction techniques and examples are discussed.

Ligamentataxis/Traction

The mainstay of indirect reduction remains skeletal traction. I recommend a distal femoral Steinman pin placed near the metadiaphyseal junction in the distal femur. This may be placed preoperatively upon the patient’s arrival to the hospital or intraoperatively. A small 2 mm K-wire with a Kirschner bow or a 5/32″ smooth Steinman pin may be used. Traction may be taken off the end of the operative table via specialized attachment or sterile Kerlix and standard weights (Fig. 7.12a–c). Traction, ligamentataxis, and indirect reduction are often the first of many planned reduction maneuvers.

../images/395168_1_En_7_Chapter/395168_1_En_7_Fig12_HTML.jpg — Fig. 7.12

(a) Preoperative AP pelvis with centrally displaced left anterior column with posterior hemitransverse acetabular fracture. Intraoperative AP view with fluoroscopy (b) before and (c) after distal femoral skeletal traction

Schanz pins placed from the lateral aspect of the greater trochanter and into the femoral head via the femoral neck may also be placed. This may be especially helpful with a “central,” or medial, displacement or dislocation of the femoral head; however I find it is rarely needed to lateralize the femoral head. Biplanar fluoroscopy should be used for placement of this pin to ensure it is contained within the femoral neck and head and there are attachments available for standard radiolucent tables to maintain this position.

Traction tables may also be used with a perineal post; however complications from prolonged pressure can develop including pudendal nerve injury, soft tissue necrosis, and well-leg compartment syndrome [30]. I do not recommend the use of traction against with a perineal post and personally use a flat radiolucent table for percutaneous reduction and fixation of acetabular fractures.

Lag by Design/Lag by Technique

Lag screws, either be technique or design, can be used in any of the corridors to aid with reduction of fractures, but the corridors and obliquity of the fracture lines must be perpendicular if the surgeon desires excellent reduction. Lag screws may be and usually are combined with any of the reduction techniques described below to create better perpendicular trajectories for compression.

While the bony corridors for the posterior column, LC-2, and magic screw allow for significant variability in the starting point and trajectory of screw placement, the corridor for the anterior column screw typically allows little variability in the trajectory of screw placement. Large diameter partially threaded cannulated screws are frequently used to compress fracture lines and all threads must cross the fracture line before compression can occur. Alternatively, fully threaded screws are employed if compression is not desired. Some bony corridors, especially that of the anterior column, require smaller diameter screws which may not be available in sufficient lengths as cannulated screws. With non-cannulated screws, a blunt tip more easily deflects off of the endosteal limit to prevent extrusion when compared with a self-tapping screw (Fig. 7.13a–b).

../images/395168_1_En_7_Chapter/395168_1_En_7_Fig13_HTML.png — Fig. 7.13

(a) A 4.5 mm blunt cortical screw approaches the cranial limit of the superior ramus prior to (b) deflecting and remaining in the osseous corridor of the anterior column. Note also the use of external fixation and a joker elevator for reduction

The starting point and the trajectory of the screw are critical if lag screw reduction is planned. It is also crucial that the head of the screw is not intruded through the cortical bone at the starting point as the screw is docked, as compression will be lost. Washers may be used to prevent intrusion of a screw head or “rescue” a screw that has been intruded, but do not usually sit flush with the cortical bone for antegrade anterior or posterior column screws (Fig. 7.14a), and are not routinely recommended. A washer generally sits flush with the AIIS with an anterior to posterior LC-2 screw (Fig. 7.14b) or with the lateral ilium with a “magic” screw and can be used at the surgeon’s discretion.

../images/395168_1_En_7_Chapter/395168_1_En_7_Fig14_HTML.jpg — Fig. 7.14

(a) Postoperative obturator oblique view after limited open reduction and antegrade anterior and posterior column screw fixation where washers were used. The cortices of the inner and outer table are highlighted in yellow demonstrating that the washers do not seat flush with the bone. (b) Fluoroscopic iliac oblique after placement of an anterior to posterior LC-2 screw with a washer

Lag screws, as an isolated reduction method, are rarely used unless a fracture component is minimally displaced. They are most commonly the final step in the reduction sequence, and osteopenia further limits their power to affect a reduction losing purchase. LC-2 screws can be used to compress fractures lines of the anterior column extending cranially into the iliac wing and the trajectory may be aimed cranial to or toward the greater sciatic notch [31] based upon the obliquity of the fracture line.

Anterior column screws best compress fracture lines through the more anterior caudal portions of the anterior column that exit anteriorly at or just lateral to the iliopectineal eminence. These are frequently seen in fracture patterns with transverse components. Posterior column screws are generally used for posterior portions of transverse components or isolated posterior column injuries, which are infrequent in younger [4] and older populations [12–14]. The location of the posterior column fracture line should dictate the starting point of the screw; fracture lines exiting at the level of the ischial spine are better treated with a retrograde starting point as ending the screw in the caudal ischium is difficult from an antegrade starting point as previously discussed. The “magic” screw is rarely used as a lag screw in elderly patients as comminution and impaction prevent compression.

When the anterior and posterior columnar segments have not been separated and are both displaced, reduction of the one column may gap the other. In these cases, alternating compression across both columns with two screws is recommended. In a T-type fracture, the anterior and posterior columns are separated, and each column is independently compressed.

Manipulative Reduction Aids

Various tools allow the surgeon to directly manipulate fragments through percutaneous incisions or limited portions of the lateral window. Great care must be taken with any instrument placed onto or into bone when direct visualization of surrounding soft tissues is not achieved.

Schanz pins can be percutaneously inserted into the bone using fluoroscopic guidance using common pin sites for pelvic external fixation. Crest pins start near the gluteus medius pillar and are directed caudally avoiding the acetabulum and any fracture lines (Fig. 7.15a). Anterior pins are placed using the same corridor of bone as the LC-2 screw and thoughtful positioning is mandatory if an LC-2 screw or anterior column screw is planned (Fig. 7.15b). A T-handle chuck is attached to the pin to allow for manipulation of fracture fragments. Ball-spike pushers percutaneously placed onto the lateral ilium may be needed when associated sacroiliac joint injury externally rotates the iliac wing.