Introduction: Potential benefits cited for minimally invasive total hip arthroplasty (THA) include reduced peri-operative blood loss, less post-operative pain, earlier mobilisation and a shortened hospital stay. Sceptics, however, are concerned about the widespread introduction of a new surgical technique in the absence of objective scientific evidence. The ever-increasing pressure on healthcare budgets by an ageing population makes developments in surgical technique that allow earlier mobilisation and reduced length of hospital stay highly desirable. The aim of this study was to investigate whether a minimally invasive technique in THA would result in a reduced length of hospital stay compared to a standard incision of 16cm.

Materials and Methods: 219 patients were randomised to either a minimally invasive (less than or equal to 10cm) or standard (16cm) incision group. Patients were blinded to their incision length. Anaesthetic and post-operative analgesic protocols were standardised. A single surgeon performed all operations using an uncemented cup and a cemented stem. Post-operative physiotherapy was standardised with the physiotherapists also blinded to incision length. Patients were discharged when safely able to transfer and mobilise with a walking aid.

Results: There was no statistically significant difference in mean length of stay following surgery. This was 3.65 days (SD 2.04) for the mini-incision group and 3.68 days (SD 2.45) for the standard incision group (p=0.94). 32% of patients (35/110) in the standard incision group were able to go home on day 2 compared to 27% (29/109) in the mini-incision group. Using logistic regression analysis, the patient variables most significantly associated with a probability of discharge within 3 days of surgery were patient age (Wald=33.36, p< 0.0001) and pre-operative haemoglobin (Wald=10.53, p=0.001).

192 patients (88.5%) were discharged to their own homes with the main determinant of discharge to the patients’ own home being the availability of adequate family support.

Conclusion: Total hip arthroplasty performed through a single incision minimally invasive approach does not reduce the length of hospital stay compared to THA performed through a standard incision of 16cm.

Introduction: Surgical injury induces a systemic inflammatory response proportional to the severity of the insult. An appropriate response maintains homeostasis and allows wound healing while an excessive response may trigger an inflammatory cascade resulting in the systemic inflammatory response syndrome (SIRS). Tissue injury results in cytokine release, which in turn stimulates the production of acute phase proteins such as C-reactive protein (CRP), fibrinogen, complement C3 and haptoglobin. Serum CRP levels rise following total hip arthroplasty (THA), peaking on the second to third post-operative day. Local effects of the inflammatory response manifest as the cardinal signs of inflammation, which include swelling.

One of the potential benefits cited for minimally invasive THA is reduced soft tissue trauma resulting in less post-operative pain, less swelling and earlier mobilisation. Objective evidence, from well designed prospective studies, for these benefits remains lacking. The aim of this study was to investigate whether a minimally invasive technique in THA results in a reduced acute phase response and reduced post-operative swelling compared to THA performed through a standard incision of 16cm.

Materials and Methods: 219 patients were randomised to either a minimally invasive (less than or equal to 10cm) or standard (16cm) incision group. Patients were blinded to their incision length. Anaesthetic and postoperative analgesic protocols were standardised. A single surgeon performed all operations using an uncemented cup and a cemented stem. Baseline CRP levels were measured pre-operatively and re-measured on the second post-operative day to determine whether there was any difference in the magnitude of the inflammatory response between the two patient groups. Pre-operative measurements were also made of the mid-thigh circumference on the affected side. The mid-thigh circumference was re-measured at 48 hours to assess postoperative swelling.

Results: There was no statistically significant difference in the mean serum CRP levels at 48 hours, which were 135.7mg/L (SD 51.2) for the mini-incision group and 125.6mg/L (SD 59.4) for the standard group (p=0.20). With respect to post-operative swelling, the mean increase in mid-thigh circumference at 48 hours was 4.3cm for the mini-incision group and 3.7cm for the standard group. The difference between the two groups was not statistically significant (p=0.30)

Conclusion: THA performed through a single incision minimally invasive approach does not result in reduced post-operative swelling or a reduced acute phase response, as measured from post-operative CRP rise, compared to THA performed through a standard incision of 16cm.