Vascular Injury in Hip & Knee Arthroplasty

Vascular injury is a rare complication of hip and knee arthroplasty, but it is potentially limb- and life-threatening. Because it is uncommon, a high index of suspicion and a low threshold for vascular imaging and specialist involvement are essential.

The knee. In total knee arthroplasty the vessel at risk is the popliteal artery, which lies just posterior to the knee. It can be lacerated directly during posterior capsular release or bone cuts, during osteophyte excision, or by a posterior retractor.

The tourniquet. The second knee mechanism is ischaemic. In a patient with peripheral arterial disease or a heavily calcified, atherosclerotic popliteal artery, the tourniquet can disrupt plaque and cause thrombosis or embolism. How to screen for these patients, and what to do with the tourniquet, is set out below.

Anatomic variants. A high popliteal bifurcation or an aberrant, anteriorly positioned anterior tibial artery (prevalence around 0.4-6%) brings the artery closer to the operative field, especially in women. Awareness of the variants and selective preoperative vascular imaging, including review of any existing MRI, may reduce the risk.

The hip. In total hip arthroplasty the external iliac, common femoral and profunda femoris vessels are at risk. The classic mechanism is an acetabular screw placed in the dangerous anterior quadrants. Retractor placement near the corona mortis, cement extrusion, and revision or protrusio surgery with intrapelvic components are the others.

"Rare but devastating" is true and unhelpful at the bedside. The numbers change three things: how hard to look, whom to look at hardest, and for how long.

The incidence. In a prospectively collected multi-institutional dataset of 41,633 arthroplasties, arterial injury occurred in 34 patients, 0.08 percent overall. That is roughly one in a thousand or fewer, and revision lifts it to about 0.2 percent for either joint, roughly double to treble the overall rate:

• Primary TKA - 0.08 percent
• Revision TKA - 0.19 percent
• Primary THA - 0.04 percent
• Revision THA - 0.20 percent

A single high-volume community system separately found 13 vascular complications in 9,951 knees (0.13 percent), consistent with the pooled picture.

What predicted it. On logistic regression a redo (revision) procedure was a significant predictor, with an odds ratio of 2.7 (95 percent CI 1.2 to 6.0). That is the measured procedural risk factor, and it maps onto the mechanisms already known: scarred planes, distorted anatomy, intrapelvic components and longer retraction.

The demographic associations. The same analysis reported African American race with an odds ratio of 2.5, and the single-centre series a striking relative risk in Black women. These rest on 34 and 13 events respectively and are unadjusted for comorbidity, vascular disease burden and access to preoperative vascular assessment, so they must not be read as biological risk. Treat them as a prompt to examine every patient's vessels properly, not as a patient category.

When it declares itself. Of the 34 arterial injuries, 18 were repaired on the day of the index operation, 8 between postoperative days 1 and 5, and 8 between days 6 and 30. Almost half therefore became apparent after the patient left theatre, and nearly a quarter after the first postoperative week.

Outcome. Where injuries were detected early and repaired, limb salvage was excellent: only 2 of the 34 (5.9 percent) came to amputation. The catastrophic outcomes follow delay rather than the injury itself.

Constructing the quadrants. Draw a line from the anterior superior iliac spine through the centre of the acetabulum to the posterior fovea, then a second line perpendicular to it at the acetabular centre. This divides the acetabulum into four quadrants, each with its own structures behind it:

• Anterosuperior - the external iliac artery and vein; the most dangerous, where a screw can be catastrophic
• Anteroinferior - the obturator artery, vein and nerve
• Posterosuperior - the sciatic nerve and the superior gluteal vessels and nerve
• Posteroinferior - the sciatic nerve and the inferior gluteal and internal pudendal vessels

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The rule. Place acetabular screws in the posterior quadrants, which have both the best bone stock and the safest depth; the posterosuperior quadrant is the preferred primary screw zone. Avoid the anterior quadrants, where the external iliac and obturator vessels lie a short distance from a screw tip that perforates the medial wall.

When the landmarks shift. Keep screws short and angled to avoid intrapelvic penetration. In revision, protrusio or dysplastic anatomy the landmarks shift, so a preoperative CT and a low threshold for navigation help, and revision is also the procedure measured to raise arterial-injury risk. Nerve-specific injury in hip replacement is developed in neurovascular injury in total hip arthroplasty.

The two errors to avoid with vascular injury in arthroplasty are missing it and delaying treatment.

Delayed injury. A pseudoaneurysm or arteriovenous fistula can present weeks to years later, with swelling, a pulsatile mass, a bruit or thrill, or distal ischaemia. A new pulsatile mass, bruit or distal ischaemia around a replaced joint warrants imaging.

Investigate and act urgently. Involve vascular surgery immediately. Obtain CT angiography, or on-table angiography, unless the limb is critically ischaemic and needs immediate exploration.

Treatment. The injury is treated by one of:

• Direct repair or bypass
• Endovascular treatment with a covered stent, particularly effective for pseudoaneurysm and AV fistula

After revascularisation, watch for and treat reperfusion/compartment syndrome with fasciotomy. Prevention, through the screening, tourniquet and screw-placement measures above, is far better than managing the catastrophe.

Screen before the incision. Palpate the distal pulses, ask about claudication and rest pain, and look for the signs of peripheral arterial disease: hair loss, trophic skin, prior bypass scars. Heavily calcified vessels on the plain radiograph are a red flag, but a clean radiograph does not exclude the at-risk vessel: only 4 of the 13 knees in the community-system series had calcification visible beforehand.

When PAD is suspected. Where pulses are absent or PAD is suspected, obtain an ankle-brachial index and an arterial duplex or CT angiography, and get a vascular surgery opinion. If there is significant occlusive disease, revascularise first and defer the elective arthroplasty.

The tourniquet decision in TKA. In a limb with PAD, a heavily calcified popliteal artery or a previous arterial bypass graft, a tourniquet risks plaque disruption, thrombosis or graft occlusion. In these patients avoid the tourniquet, or use it without forcible exsanguination, at a lower cuff pressure and for the shortest time. Over a bypass graft or a severely calcified vessel it is effectively contraindicated. General tourniquet physiology and complications are developed in tourniquet use.

Check perfusion at the end. A tourniquet can mask arterial injury and bleeding until it is released. Document the distal pulses and limb perfusion after deflation and before leaving theatre; a newly pulseless or ischaemic foot is a vascular emergency, not a "cold leg".

Keep checking after theatre. Deflation is the first check, not the last. With almost half of arterial injuries declaring after the day of surgery, distal perfusion belongs on the daily postoperative check, and a new pulse deficit, disproportionate pain, an expanding haematoma or a falling haemoglobin days after an uneventful arthroplasty warrants imaging rather than reassurance.