Outpatient / Same-Day / Rapid-Recovery Arthroplasty

Definition. Length of stay for hip and knee arthroplasty has fallen dramatically. Outpatient (same-day) and rapid-recovery arthroplasty, meaning discharge on the day of surgery or within ~23 hours, is now an established option, and the whole approach is built on enhanced recovery after surgery (ERAS) principles.

Why it has grown. Three forces drive it: advances in peri-operative and intra-operative management, especially anaesthesia, analgesia and blood management; patient demand; and financial and system incentives. With them has come a shift of selected cases to ambulatory surgery centres.

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The bundle spans the whole pathway, from pre-operative preparation to discharge.

The logic. Each element removes a barrier to early discharge. Spinal anaesthesia and multimodal, periarticular analgesia control pain with less opioid, so there is less nausea and sedation; tranexamic acid limits blood loss and the need for transfusion; avoiding drains and catheters, and giving PONV prophylaxis, removes tethers and sickness.

Mobilisation closes the loop. Early mobilisation confirms that the patient is safe to go home. The result is a patient who can meet the discharge criteria (mobile, pain and nausea controlled, voiding, observations stable) on the day of surgery.

The knee: which nerves you are willing to switch off. For the knee, one analgesic choice does more work than the rest of the bundle combined. A femoral nerve block gives excellent analgesia and paralyses quadriceps. A patient who cannot extend the knee against gravity cannot stand safely, cannot climb stairs and is at real risk of falling, so the block that controls the pain also prevents the discharge; this is why early attempts at rapid-recovery knee replacement stalled.

The adductor canal block. Sited in the mid-thigh, it targets the saphenous nerve and the sensory articular branches while largely sparing the motor supply to quadriceps. It delivers comparable analgesia with preserved extensor strength, so the patient can weight-bear and mobilise on the day of surgery. It is normally combined with local infiltration analgesia around the capsule and posterior structures, which the block does not reach.

The good candidate. Selection is what keeps the pathway safe, and the ideal patient is younger and healthier, ASA I-II.

• Motivated, understands the pathway, and has good social and home support
• No significant cardiopulmonary disease, an acceptable BMI and no untreated obstructive sleep apnoea (OSA)
• Lives within reasonable distance of the centre

Caution, or less suitable. These features count against a same-day pathway.

• ASA III-IV, significant comorbidity or frailty
• Poor social support, or living far away
• A history suggesting high risk of the failure modes (orthostatic hypotension, PONV, retention)
• Patient or surgeon/centre inexperience with the pathway

The evidence in selected patients. In carefully selected patients operated on by experienced surgeons in major centres, outpatient arthroplasty may be safe and effective. A systematic review of ~1000 patients found ~95% were discharged the same day as planned, with no deaths, only one major complication, and reoperation and readmission/ER rates of ~2% each within 90 days; the great majority said they would choose outpatient surgery again.

The caveats. The figures carry selection bias and depend on an experienced team and protocol. The data do not justify outpatient surgery for unselected patients.

Why discharge fails. In meta-analysis, the commonest reason a planned same-day discharge fails is orthostatic hypotension, followed by inadequate physical condition, nausea and vomiting, pain and urinary retention. That list is exactly why the ERAS bundle targets fluid status, opioid-sparing analgesia and PONV.

Who fails. The same meta-analysis identifies patient and anaesthetic risk factors, and one protective factor, spinal anaesthesia.

Reducing failure. Anticipating and managing these factors improves same-day-discharge success: optimise fluids, use spinal anaesthesia, minimise opioids, and manage PONV and voiding.

ASA class alone is too blunt. Selection is better operationalised with a validated, structured score and a targeted look at the specific failure-mode risks.

The OARA score. The Outpatient Arthroplasty Risk Assessment is a comorbidity-based score that weights medical conditions across multiple organ systems, and is far more granular than the ASA grade. It has been shown to predict safe same-day discharge more accurately than ASA class or age alone, and a lower OARA total identifies appropriate outpatient candidates.

The RAPT. The Risk Assessment and Prediction Tool is a short pre-operative questionnaire covering age, sex, walking distance, use of gait aids, and community and home support. It predicts the likely discharge destination and the need for inpatient rehabilitation, flagging the patients who will not go straight home.

The targeted look. Alongside the score, check for the specific failure-mode risks: untreated obstructive sleep apnoea, cardiopulmonary disease, a history of orthostatic hypotension, PONV or urinary retention, frailty, and poor home support.

General pre-operative optimisation is covered in the Arthroplasty Pre-operative Optimization topic; the point here is the same-day-discharge selection score.

Objective criteria. Same-day discharge requires meeting objective criteria, confirmed before the patient leaves, with a defined safety net behind the quoted readmission rate.

• Independent, safe mobilisation and transfers (and stairs if needed), with physiotherapy sign-off
• Pain controlled on oral analgesia; no or controlled PONV; able to void, or a clear plan for retention
• Stable observations with no orthostatic hypotension on standing; tolerating oral intake
• A responsible adult at home, often formalised with a discharge-scoring system (e.g. a modified post-anaesthetic discharge scoring system)

Why the safety net matters. The patient leaves before the window in which an early complication (bleeding, VTE, infection, a fall, retention) would otherwise have been caught in hospital. The post-discharge safety net is therefore as important as the criteria.

What the safety net contains. Written instructions and VTE prophylaxis, a same-day or next-day follow-up call or remote/virtual monitoring, clear escalation pathways with 24-hour contact, and rapid readmission access. All of it is aimed at preventing failure to rescue.