Hemiarthroplasty Hip — Indications

Hemiarthroplasty of the hip replaces the femoral head alone, leaving the native acetabulum intact. It is predominantly used for displaced intracapsular neck of femur (NOF) fractures in elderly patients where the blood supply to the femoral head has been disrupted and avascular necrosis is inevitable. The key decision in displaced intracapsular NOF fracture management is whether to perform hemiarthroplasty, total hip arthroplasty (THA), or internal fixation — a decision driven by patient age, functional status, pre-existing hip pathology, and operative risk.

• Primary indications for hemiarthroplasty: displaced intracapsular NOF fracture (Garden III or IV) in elderly, lower-demand patients; pathological fracture through a femoral head lesion where THA is not appropriate; acute femoral head fractures (Pipkin fractures) not amenable to fixation in older patients; femoral head osteonecrosis in low-demand elderly patients as a salvage procedure
• The distinction between hemiarthroplasty and THA for displaced NOF fracture hinges on: pre-fracture mobility and functional level, cognitive status, acetabular cartilage integrity, biological age, and surgeon/unit preference based on available evidence
• NICE guidance (UK): THA is recommended for patients with displaced intracapsular NOF fracture who were independently mobile (with or without a walking aid), not cognitively impaired, and are medically fit for the procedure; hemiarthroplasty is recommended for patients who are not independently mobile or are cognitively impaired; this guidance reflects the evidence from the HEALTH and HOPE trials

• Evidence comparing unipolar vs bipolar: randomised trials and meta-analyses show no significant difference in functional outcome, pain, or complication rates between unipolar and bipolar hemiarthroplasty at medium-term follow-up; bipolar is more expensive but offers no proven clinical advantage in most studies; unipolar remains appropriate for the frailest patients

• Cemented hemiarthroplasty: the preferred fixation method for most elderly patients with displaced NOF fracture; evidence from multiple RCTs and meta-analyses (including the NICE guidance) demonstrates superior functional outcomes and lower revision rates with cemented fixation compared to uncemented; cemented fixation provides immediate post-operative stability, allowing early weight-bearing; particularly important in the osteoporotic bone typical of this patient population
• Uncemented (press-fit) fixation: used in younger, higher-demand patients with better bone quality where cementless osseointegration is anticipated; in elderly osteoporotic patients, uncemented stems have higher rates of peri-prosthetic fracture, thigh pain, and subsidence; the NICE guideline recommends cemented fixation for hemiarthroplasty in elderly patients with NOF fracture
• Bone cement implantation syndrome (BCIS): a life-threatening complication of cemented arthroplasty, particularly in elderly patients with NOF fracture; occurs at the time of cement insertion and stem pressurisation; features: hypotension, hypoxia, arrhythmia, and cardiac arrest; caused by fat embolism, cement monomer absorption, and air embolism; BCIS is classified Grade 1–3 (Grade 3 = cardiovascular collapse/death); pre-operative risk assessment, careful anaesthetic monitoring, and venting of the femoral canal can reduce the risk

• Posterior approach (Moore or Southern approach): most widely used approach for hemiarthroplasty in the UK; extensile; excellent visualisation; higher dislocation rate (posterior capsule and short external rotators are divided); soft tissue repair of the posterior capsule and short external rotators (posterior repair/capsulorrhaphy) reduces dislocation rate significantly; precautions — avoid hip flexion >90°, adduction, and internal rotation post-operatively
• Anterolateral approach (Hardinge / Watson-Jones): splits the anterior part of the gluteus medius and the anterior capsule; lower posterior dislocation rate; risk of abductor weakness (Trendelenburg limp) if gluteus medius damage occurs; technically more demanding in obese patients
• Dislocation after hemiarthroplasty: the most common serious early complication; occurs in approximately 2–6% of cases; higher with posterior approach without soft tissue repair; risk factors — cognitive impairment (unable to follow precautions), neuromuscular disorders, revision surgery, poor soft tissue repair, malpositioning of the stem (excessive anteversion or retroversion); management: closed reduction under GA or sedation; if recurrent, revision to constrained liner or THA with dual-mobility cup
• Direct anterior approach (DAA): increasingly used for THA; less commonly used for hemiarthroplasty in the NOF fracture setting due to patient positioning requirements and the difficulty of fracture exposure; can be used in specialist centres

• HEALTH trial (NEJM 2019): the largest RCT comparing THA vs hemiarthroplasty for displaced intracapsular NOF fracture in ambulatory patients; found no significant difference in functional outcomes (WOMAC score) at 24 months between THA and hemiarthroplasty in this group; THA had a higher dislocation rate (7% vs 4%); this trial tempered the enthusiasm for routine THA in all ambulatory patients and re-emphasised the importance of patient selection

• Dislocation: most common early serious complication (2–6%); posterior approach higher risk without capsular repair; management — closed reduction; revision if recurrent
• Acetabular erosion (protrusio): long-term complication of hemiarthroplasty; the metal head erodes the native acetabular cartilage over years; produces pain, stiffness, and progressive protrusio acetabuli; incidence increases with time and activity level; revision to THA required for symptomatic erosion; more common with unipolar heads
• Peri-prosthetic fracture: more common with uncemented stems in osteoporotic bone; Vancouver classification for peri-prosthetic fractures around hip arthroplasty stems (A — trochanteric, B1/B2/B3 — around stem, C — distal to stem)
• Infection: deep peri-prosthetic joint infection (PJI); risk factors — diabetes, immunosuppression, obesity, prolonged operative time; managed with DAIR (debridement, antibiotics, implant retention) for early infection; single or two-stage revision for established infection
• Bone cement implantation syndrome: at time of cementation; potentially fatal; careful monitoring and venting reduce risk
• Leg length discrepancy: technical complication; templating and intra-operative assessment (use of trial components) minimises risk

• Dual-mobility cups in hemiarthroplasty: increasingly used at revision or in high-risk dislocation cases; a dual-mobility cup consists of a standard acetabular shell with a large-diameter polyethylene liner in which a smaller femoral head articulates; this creates two bearing interfaces and a very large effective head size, dramatically reducing the risk of dislocation; the large effective head must jump out of the socket at both interfaces to dislocate; increasingly used as the acetabular component when converting hemiarthroplasty to THA for acetabular erosion, or as primary THA in high dislocation risk patients
• Conversion of hemiarthroplasty to THA: required when symptomatic acetabular erosion develops years after hemiarthroplasty; technically more demanding than primary THA — the acetabulum is often eroded and deepened (protrusio), requiring bone grafting (impaction grafting or structural graft); the femoral stem may be well fixed and not require revision if functioning well; planning must account for potential femoral stem retention vs revision
• Timing of surgery for NOF fracture: surgery within 36–48 hours of admission reduces mortality and complication rates; the Blue Book (BOAST guidelines) and NICE recommend surgery on the day of or the day after admission; delay beyond 48 hours significantly increases 30-day mortality, pressure sore risk, and length of stay; medical optimisation should not delay surgery unnecessarily
• Posterior capsular repair: the Southern approach (posterior) divides the posterior capsule and short external rotators (piriformis, obturator internus, gemelli); careful repair of these structures at closure reduces dislocation rate from approximately 6% to 2–3%; the repair should be robust — transosseous sutures through drill holes in the posterior greater trochanter provide the most secure repair

• Hemiarthroplasty indications: displaced intracapsular NOF fracture (Garden III/IV) in elderly low-demand patients; cognitively impaired; not independently mobile pre-fracture; high operative risk
• THA indication in NOF fracture: independently mobile + cognitively intact + medically fit (NICE); superior function vs hemi in active patients but higher dislocation risk
• HEALTH trial (NEJM 2019): largest RCT — no significant functional difference between THA and hemi at 24 months in ambulatory patients; THA had higher dislocation rate (7% vs 4%); reinforced careful patient selection
• Cemented fixation: preferred in elderly osteoporotic bone; immediate stability; NICE recommended; lower revision and subsidence rates vs uncemented
• Bone cement implantation syndrome (BCIS): hypotension + hypoxia + arrhythmia at cementation; fat embolism + monomer absorption; potentially fatal; Grade 1–3; vent the canal; careful monitoring
• Dislocation: most common early complication (2–6%); posterior approach without repair = highest risk; posterior capsular repair reduces risk to ~2–3%
• Acetabular erosion (protrusio): long-term complication; unipolar > bipolar; revision to THA required when symptomatic; dual-mobility cup at revision
• Bipolar vs unipolar: no proven clinical advantage for bipolar in RCTs; more expensive; widely used; both acceptable
• Surgery timing for NOF fracture: within 36–48 hours; delay >48 hours increases mortality; NICE and BOAST guidelines
• Posterior approach: most common for hemi; excellent exposure; divide posterior capsule + short external rotators; repair all structures at closure to reduce dislocation