2 The procedure
2.1.1 Disability arising from hip pain is common and is usually caused by osteoarthritis. Conservative treatments include medication (antiinflammatories and analgesics) and physiotherapy. If conservative treatments fail, hip resurfacing or a hip replacement may be necessary.
2.1.2 A traditional hip replacement involves accessing the joint through a large incision (approximately 20–30 cm in length) with division of muscles, ligaments and tendons. Several different approaches may be used.
2.2.1 Minimally invasive total hip replacement is carried out with the patient under general or epidural anaesthesia, using an approach that aims to avoid damage to the muscles and tendons around the hip joint. A single incision of 10 cm or less in length is made. Alternatively, incisions are made at the front and back of the hip. Division of muscles may be necessary but is less extensive than in standard approaches. Specially designed retractors and customised instruments are typically used to expose the hip joint, prepare the acetabular socket and the femur, and insert the prosthesis. A specialised operating table may also be used. Fluoroscopic guidance and computer-assisted navigation tools may be used to aid positioning of the implant.
2.2.2 A range of different prostheses are available for this procedure, which may be cemented or uncemented.
Sections 2.3 and 2.4 describe efficacy and safety outcomes from the published literature that the Committee considered as part of the evidence about this procedure. For more detailed information on the evidence, see the overview .
2.3.1 A systematic review of 1205 patients reported that there was no significant difference in the mean change of Harris hip score (which assesses functional ability and hip dynamics, scored from0 to 100, higher scores better) from baseline in patients treated by mini-incision total hip replacement (n = 597) compared with those treated by the standard-incision approach (weighted mean difference [WMD] 3.99) (95% confidence interval [CI] –0.18 to 8.16) (p = 0.06) (follow-up not stated). A case series of 759 patients (1000 hips) reported that the mean Harris hip score improved from 34 points at baseline to 92 points at a mean 37-month follow-up (significance not stated).
2.3.2 A randomised controlled trial of 219 patients treated by mini-incision or standard-incision hip replacement reported that 85% (88/103) and 91% (96/105) of patients respectively were able to 'mobilise' the day after the operation (p = 0.54).
2.3.3 The systematic review of 1205 patients reported that mean length of hospital stay was significantly shorter after minimally invasive procedures than after standard-incision procedures: WMD –3.59 (95% CI –5.69 to –1.50) (p = 0.0008).
2.3.4 The Specialist Advisers listed key efficacy outcomes as long-term functional result, length of hospital stay, requirement for analgesics, and blood loss.
2.4.1 Revision surgery was required in 1 patient in a case series of 400 hips at 18-month follow-up, in 2% (21/1000) of hips in the case series of 759 patients at a mean 37-month follow-up, and in 9% (8/90) of hips in the case series of 70 patients at a mean 11-year follow-up.
2.4.2 The systematic review of 1205 patients reported that the overall rate of complications was not significantly different between patients treated by minimally invasive surgery and those who had standard-incision procedures: odds ratio 1.08 (95% CI –0.59 to 1.97) (p = 0.81) (follow-up not stated).
2.4.3 Deep vein thrombosis or pulmonary embolism was reported in 1% (12/1000) of the hip procedures in the case series of 759 patients at a mean follow-up of 37 months.
2.4.4 The UK National Joint Registry reported rates of calcar crack (femoral crack around the insertion of the prosthesis) of less than 1% (95/19,041) in patients treated by the procedure and less than 1% (1185/306,625) in patients treated by surgery using a standard approach. The rates of femoral shaft fracture were less than 1% (10/19,041 and 192/306,625 respectively) at follow-up of 0.1 to 6.5 years. Trochanteric fracture occurred in less than 1% (29/19,041) and less than 1% (622/306,625) of patients respectively.
2.4.5 The case series of 759 patients (1000 hips) reported heterotopic ossification in 20% (198/1000) of hips at a mean follow-up of 37-months, but none of these were high grade (grade IV) or required further treatment. The case series of 70 patients (90 hips) reported osteolysis in 11% (8/70) of hips that underwent radiographic assessment at a mean follow-up of 11 years.
2.4.6 The Specialist Advisers commented that malposition of components leading to dislocation, and femoral fracture are reported as adverse events. They considered theoretical adverse events to include neurovascular damage resulting from poor operative view.
2.5.1 Most of the evidence presented to the Committee was on single-incision minimally invasive hip replacement. The Committee saw some evidence on minimally invasive 2-incision total hip replacement (much of it mixed with evidence on single-incision surgery). They noted that the 2-incision technique is seldom used in UK practice at present. NICE has asked the National Joint Registry to collect data on 1-incision and 2-incision minimally invasive hip replacement separately, to inform any future review of these different approaches.