The following are some relevant selected scientific references:

1. A systematic review of the clinical effectiveness and cost-effectiveness and economic modelling of minimal incision total hip replacement approaches in the management of arthritic disease of the hip.

Health Technol Assess. 2008 Jun;12(26):iii-iv, ix-223.
de Verteuil R, Imamura M, Zhu S, Glazener C, Fraser C, Munro N, Hutchison J, Grant A, Coyle D, Coyle K, Vale L.
Health Services Research Unit, Institute of Applied Health Sciences, University of Aberdeen, UK.

Abstract: OBJECTIVES: To assess the clinical effectiveness and cost-effectiveness of minimal incision approaches to total hip replacement (THR) for arthritis of the hip. DATA SOURCES: Major electronic databases were searched from 1966 to 2007. Relevant websites were also examined and experts in the field were consulted. REVIEW METHODS: Studies of minimal (one or two) incision THR compared with standard THR were assessed for inclusion in the review of clinical effectiveness. A systematic review of economic evaluations comparing a minimal incision approach to standard THR was also performed and the estimates from the systematic review of clinical effectiveness were incorporated into an economic model. Utilities data were sourced to estimate quality-adjusted life-years (QALYs). Due to lack of data, no economic analysis was conducted for the two mini-incision surgical method. RESULTS: Nine randomised controlled trials (RCTs), 17 non-randomised comparative studies, six case series and one registry were found to be useful for the comparison of single mini-incision THR with standard THR. One RCT compared two mini-incision THR with standard THR, and two RCTs, five non-randomised comparative studies and two case series compared two mini-incision with single mini-incision THR. The RCTs were of moderate quality. Most had fewer than 200 patients and had a follow-up period of less than 1 year. The single mini-incision THR may have some perioperative advantages, e.g. blood loss [weighted mean difference (WMD) –57.71 ml, p<0.01] and shorter operative time, of uncertain practical significance. It may also offer a shorter recovery period and greater patient satisfaction. Evidence on long-term outcomes (especially revision) is too limited to be useful. Lack of data prevented subgroup analysis. With respect to the two-incision approach, data were suggestive of shorter recovery compared with single-incision THR, but conclusions must be treated with caution. The costs to the health service, per patient, of single mini-incision THR depend upon assumptions made, but are similar at one year (7060 pounds sterling vs 7350 pounds sterling for standard THR). For a 40-year time horizon the costs were 11,618 pounds sterling for mini-incision and 11,899 pounds sterling for standard THR. Two existing economic evaluations were identified, but they added little, if any, value to the current evidence base owing to their limited quality. In the economic model, mini-incision THR was less costly and provided slightly more QALYs in both the 1- and 40-year analyses. The mean QALYs at 1 year were 0.677 for standard THR and 0.695 for mini-incision THR. At 40 years, the mean QALYs were 8.463 for standard THR and 8.480 for mini-incision. At 1 year the probabilistic sensitivity analyses indicate that mini-incision THR has a 95% probability of being cost-effective if society’s willingness to pay for a QALY were up to 50,000 pounds sterling. This is reduced to approximately 55% for the 40-year analysis. The results were driven by the assumption of a 1-month earlier return to usual activities and a decreased hospital length of stay and operation duration following mini-incision THR. If mini-incision THR actually required more intensive use of resources it would become approximately 200 pounds sterling more expensive and would only be cost-effective (cost per QALY>30,000 pounds sterling) if recovery was 1.5 weeks faster. A threshold analysis around risk of revision showed, using the same cost per QALY threshold, mini-incision THR would have to have no more than a 7.5% increase in revisions compared with standard THR for it to be no longer considered cost-effective (one more revision for every 200 procedures performed). Further sensitivity analysis involved relaxing assumptions of equal long-term outcomes where possible. and broadly similar results to the base-case analysis were found in this and further sensitivity analyses. CONCLUSIONS: Compared with standard THR, minimal incision THR has small perioperative advantages in terms of blood loss and operation time. It may offer a shorter hospital stay and quicker recovery. It appears to have a similar procedure cost to standard THR, but evidence on its longer term performance is very limited. Further long-term follow-up data on costs and outcomes including analysis of subgroups of interest to the NHS would strengthen the current economic evaluation.

2. Early pain relief and function after posterior minimally invasive and conventional total hip arthroplasty. A prospective, randomized, blinded study.

J Bone Joint Surg Am. 2007 Jun;89(6):1153-60.
Dorr LD, Maheshwari AV, Long WT, Wan Z, Sirianni LE.
The Arthritis Institute, 501 East Hardy Street, 3rd Floor, Inglewood, CA 90301, USA.

Abstract: BACKGROUND: Few prospective randomized studies have demonstrated benefits of minimally invasive total hip arthroplasty when compared with conventional total hip arthroplasty. We hypothesized that patients treated with a posterior mini-incision would have better results than those treated with a posterior long incision with regard to the achievement of established goals for pain relief and functional recovery permitting hospital discharge by the second postoperative day. METHODS: Sixty of 231 eligible patients were randomized (with thirty in each group) to have a total hip arthroplasty performed through either a posterior mini-incision (10 +/- 2 cm) or a traditional long incision (20 +/- 2 cm). After completion of the total hip arthroplasty, the mini-incision group underwent extension of the skin incision to 20 cm. Patients were evaluated on the basis of self-determined pain scores, requirements for pain medicine, need for assistive gait devices, and time until discharge. Gait analysis provided objective functional assessment. RESULTS: The average hospital stay was 63.2 +/- 13.3 hours in the mini-incision group and 73.6 +/- 23.5 hours in the long-incision group (p = 0.04). More patients with a mini-incision were discharged by the second postoperative day (p = 0.003) and more were using just a single assistive device at the time of discharge (p = 0.005). As scored on a verbal analog scale of 0 to 10 points, patients with a mini-incision had less pain on each postoperative day and the pain score remained significantly lower at the time of discharge (mean, 2.2 +/- 1.0 points compared with 3.1 +/- 0.9 points in the long-incision group; p = 0.002). After hospital discharge, there were no clinical differences in pain or function between the two groups of patients. CONCLUSIONS: Compared with conventional total hip arthroplasty performed through a posterior incision, posterior minimally invasive total hip arthroplasty resulted in better early pain control, earlier discharge to home, and less use of assistive devices. Subsequent evaluations at six weeks and three months showed equivalency between the clinical results in the two groups.

3.  Minimally invasive total hip arthroplasty: an overview of the results.

Instr Course Lect. 2008;57:215-22.
Duwelius PJ, Dorr LD.
St. Vincent Hospital and Medical Center, Orthopaedic and Fracture Clinic, Portland, Oregon, USA.

Abstract: Small-incision total hip arthroplasty (THA) has been shown to be safe and effective in achieving early postoperative improvements in pain and function. The comparative published reports of the two-incision, anterior, and mini-posterior techniques have defined indications for small-incision THAs. The mini-posterior approach appears to be better than the traditional posterior approach for THA in terms of early patient function and acceptance. There may be little difference among the mini-incision techniques when preoperative patient education and postoperative rehabilitation are equivalent. Correct component positioning has been consistently achieved with small-incision procedures, and short-term results are the same as those of traditional THA. The mini-posterior approach also has been shown to have psychological advantages because it allows patients to be more confident about their outcomes. New anesthesia and pain management techniques have also improved early functional results. With time and technical advances such as computer navigation, the use of minimally invasive THA will become more prevalent.

4. Minimally invasive hip replacement-–a meta-analysis.

Z Orthop Unfall. 2007 Mar-Apr;145(2):152-6.
Vavken P, Kotz R, Dorotka R.
Universitätsklinik für Orthopädie, Medizinische Universität Wien, Wien, Osterreich

Abstract: AIM: A systematic review of randomized controlled trials reporting on the comparison of minimally invasive THA and standard incision technique. METHOD: An online search in Medline, CINAHL,EMBASE, and the Cochrane Controlled Trials Register was performed. Data concerning the endpoints duration of procedure, blood loss,complications, and Harris Hip Score (HHS) were extracted and pooled using a random effects model. RESULTS: 8 Studies observing a total of 917 patients(481 MIS, 436 Std.) were included. The weighted mean difference in duration of the procedures was 4 min, which is not significant(p = 0.21). There was significantly less blood loss in the mini group (p < 0.001). The difference in increases in HHS of averagely 4.14 pts. was only borderline significant (p = 0.06). The complication odds ratio showed no significance (p = 0.71). CONCLUSION: There is only a marginal difference between these techniques. The minimally invasive total hip replacement is a variance of the standard procedure with better cosmesis. Differences in postoperative rehabilitation, however,are not within the scope of this study.

5. Minimally invasive total hip arthroplasty: the posterior approach.

Instr Course Lect. 2006;55:205-14.
Sculco TP, Boettner F.
Hospital for Special Surgery, New York, New York, USA.

Abstract: Minimally invasive total hip replacement is probably a misnomer and the procedure is better termed less invasive total hip replacement. The mini-posterior approach is a modification of a standard approach, with a smaller skin incision and less deep tissue dissection. The gluteus maximus tendon is not released and the quadratus femoris muscle is minimally violated. Blood loss has been documented to be less and early recovery is facilitated. Compared with the standard posterior approach, there have been fewer complications associated with the modified approach.

6. Operative and patient care techniques for posterior mini-incision total hip arthroplasty.

Clin Orthop Relat Res. 2005 Dec;441:104-14.
Inaba Y, Dorr LD, Wan Z, Sirianni L, Boutary M.
From The Dorr Institute for Arthritis Research, Inglewood, CA 90301, USA.

Abstract: Technical and patient care improvements have occurred with the posterior mini-incision total hip arthroplasty. We hypothesized that these changes would provide better results for patients. The clinical and radiographic results of 100 total hip arthroplasties done with the posterior mini incision between January 2004 and October 2004 were compared with 100 mini-incision total hip arthroplasties done between December 2001 and September 2002. There were no differences in diagnosis, age, and body mass index of the patients in each group. Component positions were not compromised in either group. There were improvements in the 2004 group with decreased hospital stay, reduction of postoperative pain and opioid analgesic use, reduced use of assistive devices, and earlier muscle recovery. In the 2004 group there were no complications of infection, dislocation, or sciatic palsy. The posterior mini-incision operation has shown improved results with experience and changes in technique and patient care treatment. Level of Evidence: Therapeutic study, Level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence.

7. Early discharge and recovery with three minimally invasive total hip arthroplasty approaches: a preliminary study.

Clin Orthop Relat Res. 2009 Jun;467(6):1431-7.
Meneghini RM, Smits SA.
Department of Orthopaedic Surgery, New England Musculoskeletal Institute, University of Connecticut Health Center, Medical Arts and Research Building, 4th Floor, #4016, 263 Farmington Avenue, Farmington, CT 06034-4037, USA.

Abstract: Purported advantages of THA performed with minimally invasive surgical approaches include less muscle damage and faster recovery. The purpose of this preliminary investigation was to determine if differences existed between minimally invasive approaches in hospital discharge and early functional recovery in THA patients with a rapid rehabilitation protocol. Twenty-four consecutive patients were randomized to one of three minimally invasive surgical approaches (two-incision, mini-posterior, and mini-anterolateral) and enrolled in an aggressive postoperative rehabilitation program. Hospital discharge, early functional milestone recovery, and validated outcome measures (SF-36, WOMAC, Harris hip score, lower extremity activity scale) were collected. All patients met hospital discharge criteria no later than the first postoperative day. There was no difference in hospital discharge, functional milestone recovery, or validated outcome measures during the first year after surgery with the numbers available. There were no complications directly related to early hospital discharge or the aggressive rehabilitation protocol. While the data suggest earlier hospital discharge and rapid rehabilitation protocols may be implemented successfully we found no difference between the three minimally invasive approaches in early hospital discharge or early functional recovery utilizing a rapid rehabilitation protocol. Level of Evidence: Level IV, therapeutic study.

8. A minimal-incision technique in total hip arthroplasty does not improve early postoperative outcomes. A prospective, randomized, controlled trial.

J Bone Joint Surg Am. 2005 Apr;87(4):701-10.
Ogonda L, Wilson R, Archbold P, Lawlor M, Humphreys P, O’Brien S, Beverland D.
Orthopaedic Outcomes Unit, Musgrave Park Hospital, Stockmans Lane, Belfast BT9 7JB, Northern Ireland, United Kingdom.

Abstract: BACKGROUND: Minimally invasive total hip arthroplasty has stirred substantial controversy with regard to whether it provides superior outcomes compared with total hip arthroplasty performed through longer incisions. The orthopaedic literature is deficient in well-designed scientific studies to support the clinical superiority of this approach. The objective of this study was to compare the results of a single mini-incision approach with those of a standard-incision total hip arthroplasty in the early postoperative period. METHODS: Two hundred and nineteen patients (219 hips) admitted for unilateral total hip arthroplasty between December 2003 and June 2004 were randomized to undergo surgery through a short incision of <or=10 cm or a standard incision of 16 cm. All patients were blinded to the size of the incision for the duration of the hospital stay. The anesthetic, analgesic, and postoperative physiotherapy protocols were standardized, with the staff also blinded to the technique used. A single surgeon, who had performed more than 300 short-incision hip replacements prior to the start of this study and who performs an average of 415 primary total hip replacements a year, performed all procedures through a single-incision posterior approach using a cementless cup and cemented stem. RESULTS: The two groups were matched for age, grade according to the system of the American Society of Anesthesiologists, and body mass index. No significant difference was detected with respect to postoperative hematocrit, blood transfusion requirements, pain scores, or analgesic use. We found no difference in early walking ability or length of hospital stay and no difference in component placement, cement-mantle quality, or functional outcome scores at six weeks. The patient variables significantly associated with a probability of early discharge independent of incision length were patient age and preoperative hemoglobin levels (p < 0.05). The surgical scars contracted significantly over six weeks (p < 0.05) but by a similar proportion of 11% to 12% in both groups. CONCLUSIONS: Minimally invasive total hip arthroplasty performed through a single-incision posterior approach by a high-volume hip surgeon with extensive experience in less invasive approaches to the hip is safe and reproducible. However, it offers no significant benefit in the early postoperative period compared with a standard incision of 16 cm. As it is not known whether lower-volume and less-experienced surgeons can achieve similar results, the mini-incision technique merits further study before wide dissemination and implementation of this family of surgical approaches can be recommended.

9. Mini-incision anterior approach does not increase dislocation rate: a study of 1037 total hip replacements.

Clin Orthop Relat Res. 2004 Sep;(426):164-73.
Siguier T, Siguier M, Brumpt B.
Clinique Jouvenet, Paris, France.

Abstract: Correct positioning of the prosthetic components in total hip replacements is important to prevent dislocations. Correct positioning is made easier by extensive approaches, but it also is possible using the mini-incision approach. The mini-incision used to facilitate early rehabilitation should not produce a higher dislocation rate than that of the more conventional approaches. The anterior surgical approach we describe allows for good exposure, despite the reduced size of the skin incision. Its length is 5-10 cm and usually 6-8 cm for patients with normal corpulence. Our mini-incision anterior approach using intermuscular planes allows a surgical approach to the hip and implantation of a total prosthesis with no muscle, tendon, or trochanteric section, even partially. This is not possible with any other surgical approach. A series of 1037 primary total hip replacements done between June 1993 and June 2000 was studied retrospectively. The dislocation rate was 0.96% (10 of 1037 hips). The mini-incision approach allows for adequate positioning of the two prosthetic components. Preserving the muscular potential also may contribute to dynamic stabilization of the hip.

10. Minimally invasive total hip arthroplasty: the Hospital for Special Surgery experience.

Orthop Clin North Am. 2004 Apr;35(2):137-42.
Sculco TP, Jordan LC, Walter WL.
Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA.

Abstract: The mini-incision technique is not a radically new technique. The surgeon familiar with the posterior approach will immediately appreciate the inherent similarities. The technique can be developed on a graduated basis by individual surgeons. The surgeon should begin by documenting the length of his or her current routine incision, and then the incision can be progressively reduced in length at a rate that is comfortable. At no time is it necessary to compromise the goals of the procedure because of inadequate visualization. The mini-incision is not for every patient. Obese individuals (BMI> 30), patients with very muscular thighs, stiff hips, or severe deformity may not be candidates for an 8-cm incision, but familiarity with this technique allows even these patients to be operated on through a smaller incision than the traditional 20-25 cm. The initial drive for shorter incisions was a result of patient concerns regarding the cosmesis of the scars and the desire for a more rapid recovery. Subsequent development of the technique and clinical analysis over the last 7 years has shown that THA can be performed safely and effectively through a mini-incision in most patients. So far the author shave found no increased risk for intraoperative or postoperative complications and no problems with component malposition. Longer follow-up is required to determine the long-term outcome; however, in the short term, patients have less blood loss, shorter operative times, and a reduced incidence of limp and cane use at 6 weeks.