Discharge on the day of surgery following unicompartmental knee arthroplasty within the United Kingdom NHS

Outpatient unicompartmental knee arthroplasty (UKA) with discharge from hospital on the day of surgery has been successfully performed in the United States healthcare system,^1,2 with studies reporting that this can be done safely and with rates of discharge of up to 100%.^1,2 UKA allows a quicker short-term recovery with reduced morbidity, reduced post-operative pain and improved outcomes compared with total knee arthroplasty (TKA).^3-5 Reduced length of stay following arthroplasty has been shown to be associated with reduced peri-operative complications, improved clinical outcomes and offers obvious financial advantages.^1,6-9

Despite differences in the healthcare system and financial environment, we hypothesised that it would be possible to replicate the success reported from centres in the United States^1,2,9 and perform UKA with safe discharge home on the day of surgery within the confines of the United Kingdom NHS. A pilot study performed in our trust in 2011¹⁰ suggested that this was possible, with six out of seven patients being successfully discharged on the day of surgery.

Outpatient UKA has not been reported in any other centres within the United Kingdom. We report our experience of implementing a pathway to allow discharge on the day of surgery following UKA.

Patients and Methods

Data were prospectively collected on 130 consecutive patients who underwent UKA in our unit between December 2011 and September 2015. Those deemed suitable for this procedure had symptoms and radiographic features of single compartment osteoarthritis and had failed conservative treatment. Patients with inflammatory arthritis, a deficient anterior cruciate ligament, a fixed flexion deformity > 15° and a non-passively correctable deformity were not offered UKA. Pre-operative investigations consisted of standard weight-bearing anteroposterior, lateral and skyline patellar radiographs of the knee.

The inclusion criteria for discharge on the day of surgery were that the patient’s medical co-morbidities were considered to be stable and their home situation allowed safe discharge with appropriate care. There were no arbitrary limitations such as American Association of Anaesthesiologist (ASA) grade,¹¹ age or body mass index.

All patients listed for UKA with discharge on the day of surgery were separately assessed by a pre-operative team including a consultant anaesthetist and specialist nurses. Co-existing medical conditions were assessed and optimised. Cardiopulmonary exercise testing was undertaken for those patients that were deemed to be at risk, and based on the results those identified as requiring a high dependency or intensive therapy unit post-operatively were excluded from the day of surgery discharge pathway.

All patients also attended an outpatient session run by a consultant orthopaedic surgeon, a team of physiotherapists and specialist orthopaedic and anaesthetic nurses. They were informed about the peri-operative plan in order to manage their expectations and reinforce the idea of day of surgery discharge. The patients were assessed again on the morning of surgery by the consultant anaesthetist supervising the operating list. They were seen by a physiotherapist and shown how to mobilise with crutches. Pre-operatively they received paracetamol (1g orally), slow release ibuprofen (1600 mg orally, if not contra-indicated) and pregabalin (150 mg). They were encouraged to drink clear fluids pre-operatively. These patients were placed first on the operating list or the operation had to have started before noon. All had general anaesthesia with propofol and remifentanil, supplemented by a sub-sartorial saphenous nerve block^12,13 performed under ultrasound control in the anaesthetic room with 20 mls 0.25% levo-bupivacaine. Our standard pre-operative antibiotic regime of gentamicin (240 mg or 3 mg/kg if body weight < 60 kg) and intravenous teicoplanin (400 mg), was given prior to induction. The use of teicoplainin avoided the requirement for further post-operative doses of intravenous antibiotics. Other intra-operative medications included tranexamic acid at induction (unless contraindicated) and intravenous fentanyl (300 mcg) at the end of the procedure.

The operations were performed by one of two surgeons (MH and DLI) using a standard minimally-invasive approach. A tourniquet was used in all patients. Two different implants were used: Oxford (Biomet, Warsaw, Indiana) and ZUK (Zimmer Biomet, Warsaw, Indiana) depending on the preference of the surgeon. Following introduction of the components, 50 ml to 60 ml of 0.25% bupivacaine with adrenaline was infiltrated into the posterior capsule, cruciate ligaments, periosteum, synovium, and skin using a 22 gauge needle.^14,15 The wound was closed in layers with a subcutaneous suture and tissue glue. A bulky dressing of wool and crepe was applied.

Post-operatively, patients were initially recovered in the main theatre and then moved to the separate day case suite. All were encouraged to drink freely, with analgesia provided in further doses of paracetamol and intravenous fentanyl or oral morphine, if required. They were seen by a physiotherapist, mobilised fully weight-bearing with crutches, and assessed using standard discharge criteria for inpatient rapid rehabilitation following arthroplasty, including: transfer from a supine to a standing position; walk > 100 feet without assistance and ascend and descend a flight of stairs. They were given an information booklet and enrolled in routine outpatient physiotherapy classes.

After these criteria had been fulfilled, radiographs were undertaken and reviewed by the surgeon. Following review by a consultant anaesthetist, the patients were discharged, with paracetamol 500 mg/codeine 30 mg (two tablets four times per day), ibuprofen 400 mg (three times per day), tramadol 50 mg (max dose 200 mg/day) and Movicol. They were given a 24-hour emergency contact number manned by the day surgery nursing team during working hours or a senior nurse out of hours. All were contacted 24 hours post-operatively by the day surgery nursing team to record pain scores, nausea or vomiting, dizziness, drowsiness and satisfaction with the process. Pain levels were assessed using a Verbal Rating Scale.¹⁶ Satisfaction was recorded using a simple descriptive scoring system¹⁷ of very satisfied, satisfied and not satisfied. The patients were reviewed at six weeks post-operatively by the operating surgeon.

Statistical analysis

This was performed on two cohorts: planned day cases and planned inpatients. Continuous data are reported with means and standard deviations, and compared using unpaired t-tests. Categorical data are reported with counts and percentages, and compared using chi-squared tests. The level of statistical significance was set at p < 0.05.

Results

A total of 72 patients met the criteria for day of surgery discharge and 58, who failed to meet the necessary requirements, underwent UKA as an inpatient. Their details are shown in Figure 1 and Table I. The mean age of the groups was significantly different (p = 0.018) but there was no significant difference in gender (p = 0.34) or ASA grade (p = 0.14).

Of the 72 patients who underwent day case UKA during the study period, 61 (85%) were successfully discharged on the day of surgery (Table II). No patient was re-admitted within a 31-day period.

The 11 patients (15%) who could not be discharged on the same day had a mean length of stay of 1.2 nights (1 to 3). The most common reason for failed discharge was a logistical problem with failure to start the operation before noon (five patients). The other reasons included failure of physiotherapy assessment, with three patients being unable to mobilise safely; two had inadequate control of pain and one had a leak from their wound, which settled following overnight admission.

Of the 58 patients who underwent planned inpatient UKA during this time, three were discharged on the same day, having met the appropriate criteria. The mean length of stay for the remaining 55 patients was 2.7 nights (1 to 7).

Table III shows the information which was obtained 24 hours post-operatively. Data were available for 70 patients. A total of 51 (73%) reported no or mild pain; 14 (20%) reported moderate pain and five (7%) reported severe pain. Of the latter five patients, four had already contacted the team through the emergency contact number and one had contacted their general practitioner. All were given advice about optimising the analgesia provided on discharge and none were re-admitted. Two patients (3%), at this time, reported nausea; the remaining 68 (97%) reported no nausea. Four (6%) had vomited once since leaving hospital and one had vomited three times. A total of 65 patients (93%) reported no vomiting. Three (4%) reported some mild dizziness and one reported mild drowsiness. A total of 41 patients (59%) reported that they were “very satisfied”, 29 (41%) were “satisfied”. No patient reported dissatisfaction with the discharge process.

Discussion

We found that patients could be discharged safely on the day of surgery after UKA within the constraints of the current United Kingdom NHS. We achieved a rate of discharge of 85% from a pre-selected series of patients with no re-admissions, and high levels of satisfaction. We are the first unit within the United Kingdom to demonstrate this.

Our day of discharge pathway, whose design was based on experience from the United States^1,2,9 and developed from a pilot study,¹⁰ was found to be safe and effective. It offers clear benefits to the patient, the healthcare trust and the NHS.

Reduced inpatient stay following arthroplasty is associated with reduced complications and results in improved clinical outcomes with high levels of satisfaction.^6,7,9 Day of surgery discharge offers trusts within the NHS better bed occupancy and use of resources, locally and nationally. We found that 15% of patients undergoing a UKA which was planned to be undertaken as a day case required admission. Trusts can use this information to predict the availability and use of beds. The current cost of inpatient care in our trust is £350 per night. As the mean length of stay for patients who failed to meet the criteria for day of surgery discharge was 1.2 nights (1 to 3) and for planned inpatient UKA was 2.7 nights (1 to 7), the financial savings from a safe and effective day of surgery discharge pathway are extensive. The opportunity to perform additional procedures which require inpatient admission as a result of the extra bed space would provide additional revenue and aid the management of waiting lists.

The most critical element to achieving discharge on the day of surgery after UKA is the timing of the procedure, which must be started before noon in order to allow the patient time to recover and to allow discharge later that day. This is reflected in the results of this study with five patients (7%) failing to meet the discharge criteria as their surgery was started too late in the day.

We also believe that the anaesthetic technique is particularly important. In accordance with pathways from the United States,^1,2,9 we used a short acting general anaesthetic in combination with the infiltration of local anaesthetic, whose benefits are well recognised in TKA.^12,13 However, our pathway differed in that we used a subsartorial saphenous nerve block¹⁴ which was administered by the anaesthetist in the anaesthetic room pre-operatively under ultrasound control. The use of this nerve block has been reported in anterior cruciate ligament reconstructions¹⁵ but has not been described for arthroplasty of the knee. In contrast to femoral nerve blocks, which are standard practice when UKA is undertaken as a day case in the United States,^1,2 a subsartorial saphenous nerve block allows immediate post-operative mobilisation without the need for a brace as it only blocks the sensory component of the femoral nerve.

Although this study showed a rate of discharge of 85% following UKA, a rate of 100% has been reported from the United States² with no pre-operative criteria for the selection of patients. This may reflect the availability of step-down non-hospital care commonly used in the United States,^1,2 but our pathway could be refined to achieve a higher rate of discharge. The most common reason for patients failing to be discharged on the day of surgery was that the operation was started too late in the day. This can be addressed through improved planning of operating lists, limiting late starts and placing day case UKAs early on the list. Two patients (3%) in our study could not be discharged on the day of surgery due to pain. The post-operative relief of pain involved oral narcotics, and improved analgesia could be provided with the addition of intravenous narcotics, as in pathways in the United States.^1,2 Three patients (4%) failed the physiotherapy discharge criteria, which are difficult to improve. A total of 58 patients underwent planned inpatient UKA during the study period as they had failed to meet the criteria for discharge on the day of surgery. However, post-operatively, three of these patients could be discharged on the same day, suggesting that the selection criteria are too stringent and could be relaxed. Whilst we feel that replicating pathways from the United States in which all patients listed for UKA are included² in day of surgery discharge pathways would be too aggressive in the United Kingdom NHS, we are planning to review our selection criteria.

Limitations of the study include the fact that we did not compare patient reported outcome measures between those discharged on the day of surgery and those treated as an inpatient, we are unaware of any negative impact of the day of surgery discharge pathway on rehabilitation. Comparison of these two groups would clearly be subject to bias as the inpatients were, by definition, considered to be in poorer health or less mobile.

In conclusion, we found that discharge on the day of surgery after UKA can be achieved safely and effectively within the constraints of the United Kingdom NHS, with high levels of satisfaction.

Take home message:

- UKA patients can be safely and effectively discharged on the day of surgery with high levels of patient satisfaction.

- Implementing a day of surgery discharge pathway for UKA offers financial savings to healthcare trusts.

Author contributions:

B. Bradley: Development and implementation of day of surgery pathway, Data collection, Processing and preparation of paper.

S. Middleton: Data collection and processing.

N. Davis: Data collection and processing.

M. Williams: Significant role in revision of paper as per reviewers’ requests.

M. Stocker: Development and implementation of day of surgery pathway, Anaesthetic lead on day of surgery pathway, Edited paper.

M. Hockings: Senior author, Development and implementation of day of surgery pathway, Performed procedures, Edited paper.

D. L. Isaac: Senior author, Development and implementation of day of surgery pathway, Performed procedures, Edited paper.

No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.

This article was primary edited by J. Scott.