Sudden Leg Deformity After Posterior Total Hip Arthroplasty
At 21:40, Ms. R, 62 years old (BMI 34, OSA, on CPAP), is 8 hours after a right total hip arthroplasty through a posterior approach under spinal anesthesia. She has a femoral nerve block and a hydromorphone PCA. While using a bedside commode she felt a sudden pop and sharp groin pain. Back in bed, the right leg is shortened by about 3 cm, internally rotated and adducted, and she will not let anyone move it. Dorsalis pedis pulse is 2+, capillary refill 2 seconds; she reports numbness over the dorsum of the right foot and cannot dorsiflex the ankle. Pain is 9/10. HR 104, BP 152/88, SpO2 94% on 2 L. The incision is dry, the calf is soft and nontender, and she has no chest pain or dyspnea. The on-call resident is in the operating room and will not be available for 30 minutes.
1. What is your first priority, and what will you do during the next 30 minutes?
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The priority is preserving the sciatic nerve and preventing further injury, not simply controlling pain. The triad of shortening, internal rotation/adduction, and a new foot drop after a posterior-approach arthroplasty points to posterior dislocation with sciatic stretch.
- Do not attempt reduction or apply traction. Manipulation by a nurse can worsen nerve injury or convert a closed injury into a fracture.
- Support the limb in its current position with pillows; avoid hip flexion beyond 90 degrees and do not force the leg into neutral.
- Escalate past the resident: page the orthopaedic attending (or the resident's backup) now, because a motor deficit is a time-sensitive surgical problem. Do not wait 30 minutes to notify someone.
- Start q15-minute neurovascular checks (sensation over the dorsal web space, dorsiflexion and plantar flexion, pulses, color, temperature) and document each.
- Keep her NPO, confirm IV access, send type and screen, and prepare consent for closed reduction under procedural sedation.
- Give analgesia but avoid heavy sedation that would blunt your ability to detect worsening nerve function.
2. How would you distinguish dislocation, periprosthetic fracture, and deep vein thrombosis in this patient? Which findings in the scenario support each?
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Dislocation (most likely): the mechanism (low commode, hip flexed past 90 degrees with adduction and internal rotation), the sudden pop, shortening, fixed internal rotation/adduction, and the immediate nerve deficit all fit. Posterior dislocation classically produces a shortened, internally rotated, adducted limb; anterior dislocation produces external rotation.
Periprosthetic fracture: possible after a fall or forced twisting, and can also shorten the leg. It is more likely with major trauma, audible crack, or inability to bear any weight, and it is confirmed on imaging. It does not usually produce the classic rotational posture, but you cannot exclude it clinically - X-ray is required before reduction.
DVT: would not shorten or rotate the limb. It causes calf swelling, tenderness, and unilateral edema, often days later. This calf is soft and nontender, making DVT unlikely as the explanation for the deformity, though she remains at VTE risk.
Key point: the posture and nerve deficit drive urgent imaging plus reduction; DVT is a later, separate concern.
3. The hip is reduced in the operating room, but the foot drop is unchanged at 24 hours. What positioning, mobility, and monitoring plan do you use now?
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Persistent foot drop after reduction means the nerve was stretched or contused; recovery is often partial and can take months, so the plan combines protection, function, and surveillance.
- Positioning: maintain posterior-hip precautions - abduction pillow or wedge, no hip flexion beyond 90 degrees, no adduction past midline, no internal rotation, no crossing the legs. Log-roll rather than twist.
- Skin and foot care: the insensate dorsum of the foot is at risk for pressure injury and burns. Inspect daily, protect with an AFO or boot as ordered, avoid heating pads, and check footwear for foreign objects.
- Mobility: physical therapy for gait training with the AFO, and teach a step-to or swing gait as needed. Falls risk rises with a drop foot, so keep the call light within reach and assist to the bathroom.
- Monitoring: continue neurovascular checks per protocol, watch for returning dorsiflexion and sensation, and document serial findings so trends are visible. Report new burning pain, allodynia, or worsening deficit - these may signal complex regional pain syndrome or progressing nerve compression.