# Complications of Total Hip Replacement > Complications of total hip replacement for NEET-PG Orthopaedics, covering dislocation, aseptic loosening, leg length, nerve injury and heterotopic ossification. - Canonical URL: https://prepelephant.com/topics/neet-pg/orthopaedics/complications-of-total-hip-replacement - Exam / course: NEET-PG · Subject: Orthopaedics - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-14 - Last updated: 2026-10-14 - Reference basis: Campbell's Operative Orthopaedics; Maheshwari's Essential Orthopaedics; Miller's Review of Orthopaedics - How to cite: "Complications of Total Hip Replacement", PrepElephant, https://prepelephant.com/topics/neet-pg/orthopaedics/complications-of-total-hip-replacement ## Direct answer Complications of total hip replacement include dislocation, aseptic loosening, leg length inequality, nerve injury and heterotopic ossification, each with a typical timing and cause. Dislocation is among the commonest early complications and is most often posterior, while aseptic loosening appears later as osteolysis from wear debris. Heterotopic ossification is graded by the Brooker classification, and the sciatic nerve is the nerve most at risk. ## What you must remember - **Dislocation:** among the commonest early complications and most often posterior, with risk linked to the posterior approach, soft tissue repair and component malposition. - **Aseptic loosening:** a late complication driven by osteolysis from particle disease, presenting as thigh or groin pain with radiolucent lines around the components. - **Leg length inequality:** true shortening reflects component position, while apparent shortening from pelvic tilt or adduction contracture is soft tissue related; true length is measured from the ASIS to the medial malleolus and apparent length from the umbilicus, with the patient supine. - **Sciatic nerve palsy:** most at risk with posterior approaches and in revision surgery, and the peroneal division usually produces foot drop. - **Heterotopic ossification:** bone formation in soft tissue around the hip, graded by Brooker from I to IV, with NSAIDs or single-dose radiotherapy used in high-risk patients. - **Infection:** early infection is often treated with debridement and liner exchange, while late infection usually needs revision surgery. - **Venous thromboembolism:** deep vein thrombosis and pulmonary embolism remain serious early risks, so prophylaxis is standard after arthroplasty. ## Managing an early posterior dislocation A 70-year-old woman falls at home two weeks after a posterior-approach total hip replacement and cannot bear weight. The leg looks shortened, adducted and internally rotated, which points to a posterior dislocation until imaging shows otherwise. 1. **Recognise the position:** a shortened, adducted and internally rotated limb with inability to weight-bear suggests posterior dislocation. 2. **Image promptly:** anteroposterior pelvis and lateral views confirm the dislocation, assess component position and exclude a periprosthetic fracture. 3. **Reduce early:** closed reduction under sedation or anaesthesia is attempted quickly, before soft tissues shorten and reduction becomes harder. 4. **Confirm stability:** after reduction, the hip is taken through a range of movement and imaging checks that the head is congruent with the socket. 5. **Find the cause:** cup or stem malposition, abductor weakness and impingement are sought, since recurrence depends on them. 6. **Protect the hip:** precautions against flexion beyond 90 degrees, adduction and internal rotation are followed for the period the surgeon sets. 7. **Revise if recurrent:** repeated dislocation prompts revision with a larger head, a dual mobility bearing or a constrained liner, as the surgeon judges. ## Where the exam tries to catch you Complication questions turn on timing, the cause and the nerve at risk. - **Trap:** reducing an early dislocation without checking component position — **Correct:** malposition is a common reason for recurrence, so imaging after reduction is essential. - **Trap:** calling leg length inequality after total hip replacement a sign of failure — **Correct:** apparent shortening from adduction is often soft tissue related, while true shortening follows component position. - **Trap:** attributing foot drop after total hip replacement to a ligament injury — **Correct:** it is a sciatic nerve palsy, most often involving the peroneal division, and needs urgent assessment. ## Frequently asked questions ### Which approach to total hip replacement carries the highest dislocation risk? The posterior approach carries a higher dislocation risk than other approaches to total hip replacement, mainly because of soft tissue repair and component malposition. Posterior dislocation is the usual direction, so precautions are given for a defined period after surgery. ### What is the Brooker classification of heterotopic ossification? The Brooker classification grades heterotopic ossification after total hip replacement from grade I to grade IV on radiographs. Grade I shows islands of bone in the soft tissue, grade II larger spurs with a gap of at least one centimetre, grade III ossification narrowing the gap below one centimetre, and grade IV ankylosis. ### Which nerve injury is most common after total hip replacement? The sciatic nerve is the nerve most often injured after total hip replacement, with the peroneal division usually causing foot drop. Risk is higher with posterior approaches and in revision surgery, so the nerve is examined before and after the operation. ### What distinguishes true from apparent leg length inequality after total hip replacement? True leg length inequality reflects a change in the bony distance from pelvis to knee, usually due to component position. True length is measured from the anterior superior iliac spine to the medial malleolus, while apparent length is measured from the umbilicus to the medial malleolus, with the patient supine; apparent inequality reflects pelvic tilt or adduction contracture.