Why the approach behind your hip replacement matters

When a surgeon recommends a total hip replacement, most patients focus on the implant — which material, which brand, how long it will last. What receives far less attention is how the surgeon actually reaches the joint, and whether that choice affects recovery speed, dislocation risk, and the need for post-operative movement restrictions.

Both SPAIRE and SuperPATH are refinements of the standard posterior approach to hip arthroplasty, not entirely different surgical routes. The implant itself is unchanged; the difference lies in what happens to the muscles and tendons the surgeon moves aside to access the joint. The standard posterior approach cuts through the short external rotator tendons — structures that help hold the hip in place — and attempts to repair them afterwards. Muscle-sparing variants such as SPAIRE and SuperPATH each aim to disturb these structures as little as possible, with the goal of reducing dislocation risk and accelerating early recovery.

The two techniques achieve this through anatomically distinct strategies, and the evidence supporting each has been built largely in separate studies. No randomised trial has yet tested them directly against one another, so any comparison rests on what each approach has demonstrated on its own terms.

How SPAIRE works — tendon preservation from inside the interval

At the back of the hip joint, a group of small muscles — the short external rotators — form something like a sling across the posterior femoral head. The standard posterior approach severs most of this sling to gain access to the joint, then attempts to repair it afterwards. SPAIRE works through the space between that sling and the joint capsule, leaving the sling intact.

The acronym maps directly onto the surgical steps: Saving Piriformis And (obturator) Internus with Repair of (obturator) Externus. The piriformis and obturator internus tendons are never divided; only the obturator externus — the lowest of the group — is released to allow exposure, and it is repaired anatomically before closure. The technique was first described in 2016 and developed at the Exeter Hip Unit, and one published series reports its use in over 1,026 consecutive primary total hip replacements.

Preserving those upper tendons does two things simultaneously. Mechanically, the intact obturator internus tendon wraps around the lesser sciatic notch and passes across the posterior femoral head, generating what is described as a 'strap effect' — a passive restraining force that resists posterior dislocation without any conscious muscular effort from the patient. Neurologically, the undisrupted tendons retain functioning Golgi tendon organs and muscle spindles that feed continuous proprioceptive signals back to the central nervous system, providing a reflexive check against extremes of range that a divided and repaired tendon cannot replicate in the early post-operative period.

The practical consequence is the immediate removal of standard hip precautions — the instructions typically given after posterior total hip replacement restricting flexion beyond 90° and prohibiting leg crossing. Because the posterosuperior stabilising structures are anatomically intact, those restrictions are unnecessary from the first day of recovery.

Published evidence supports early benefits. A systematic review of 1,385 hips found that SPAIRE offers short-term advantages in post-operative mobility and pain management over conventional approaches. A 194-case hemiarthroplasty series reported 0% dislocation in the SPAIRE group against 2% with an anterolateral approach and 3.7% with the standard posterior approach, and mean time to first mobilisation was 1.4 days compared with 2.0 and 2.6 days in the comparator groups. The approach's research trajectory includes the NIHR-funded HemiSPAIRE multicentre RCT (recruited November 2019 to April 2022) and the ongoing HIPSTER trial, a three-arm study comparing robotic-assisted SPAIRE, piriformis-sparing, and standard posterior techniques. Prof Paul Lee, whose published work on SPAIRE informs the clinical framing here, has combined the technique routinely with Mako robotic assistance since 2018, a pairing that uses intact soft-tissue tension to sharpen intraoperative judgement of leg length and offset.

How SuperPATH works — above the capsule, no dislocation needed

SuperPATH takes a fundamentally different route to the same destination. Rather than working through the interval between the short external rotators and the capsule — as SPAIRE does — it approaches from above the capsule entirely, accessing the joint through what is called the supracapsular interval: a natural anatomical window that sits above both the external rotators and the capsule itself. Because the surgeon never needs to breach that posterior soft-tissue layer, none of the external rotator tendons or capsule require division.

The most distinctive feature of the technique is that the hip joint is never dislocated during the operation. In conventional posterior approaches, the femoral head is levered clear of the acetabulum to allow preparation of the femoral canal; with SuperPATH, all femoral work is carried out in situ, through a working incision of approximately 5.8 cm. The practical effect is reduced mechanical disruption to the surrounding soft tissues and, in published data, meaningfully lower intraoperative blood loss. A 2021 network meta-analysis of 24 randomised controlled trials (2,074 patients) found SuperPATH reduced intraoperative blood loss by a mean of 157 mL compared with the direct anterior approach, and a 120-patient RCT comparing SuperPATH with the modified Hardinge approach recorded lower post-operative creatine kinase levels — a biochemical marker of muscle damage.

Those gains come with genuine technical demands. Preparing the femoral canal around an undislocated femoral head requires surgeon-specific training, dedicated positioning equipment, and instrumentation not available in every theatre. A network meta-analysis of 20 RCTs (1,501 patients) found operative time was on average 17 minutes longer with SuperPATH than with the standard posterior approach. The learning curve is steeper than for SPAIRE, whose exposure can be converted to a standard posterior field by simply extending the incision if an intraoperative complication — such as a periprosthetic fracture — requires it. SuperPATH's supracapsular geometry offers less flexibility for that kind of rapid extension, making patient and anatomical selection an important part of the pre-operative conversation.

What the evidence shows for each approach

Placing the published numbers side by side reveals where each approach wins, where the gains flatten out, and — crucially — why a direct winner cannot yet be declared.

SPAIRE outcomes

The dislocation and early mobility figures described in the previous section sit within a broader pattern of safety findings. A 2025 comparative study found no statistically significant differences between SPAIRE and the direct lateral approach on prosthesis dislocation rate, infection rate, or mortality — while the direct lateral approach carries a documented gluteal failure (Trendelenburg gait) risk of up to 20%, a complication SPAIRE avoids by leaving the posterior soft-tissue sling intact.

SuperPATH outcomes

A 2025 updated meta-analysis pooling 9 RCTs (299 SuperPATH versus 379 traditional hip replacement patients) found SuperPATH associated with significantly shorter incision length, shorter hospitalisation duration, lower post-operative pain severity, and better early hip function scores. A 2021 network meta-analysis of 24 RCTs (2,074 patients) extends that picture against a direct anterior comparator: SuperPATH reduced operative time by a mean of 8.1 minutes, incision length by 2.7 cm, and day-one VAS pain scores by 0.8 points, with acetabular cup positioning equivalent between the two minimally invasive approaches.

Where the techniques converge

Both approaches show their clearest measurable advantages within the first six to twelve months after surgery. Beyond that window, long-term functional outcomes are broadly comparable across all minimally invasive total hip replacement techniques — a consistent finding in the current literature. Because no head-to-head randomised trial has yet tested SPAIRE against SuperPATH directly, placing one above the other on clinical outcomes is not supported by the present evidence base.

Which patients suit which approach

For most patients considering primary total hip arthroplasty, SPAIRE is a realistic option at centres where a surgeon trained in the technique operates. Its exposure stays within the standard posterolateral field and can be widened without specialist table positioning if anatomy proves more demanding than pre-operative imaging suggested — a practical safety net that makes it applicable across a broad range of body types. Where it becomes more technically demanding is in patients with small anatomy, reduced femoral offset, or a significant fixed external rotation deformity; each of these narrows the working space within the posterior interval, and in those circumstances a surgeon may favour an alternative approach.

SuperPATH's suitability is shaped more by logistics than anatomy. The technique suits patients for whom avoiding intraoperative joint dislocation carries a particular surgical priority, but it depends on dedicated positioning systems and instrumentation that are not standard in most UK orthopaedic theatres. Surgeons trained in the supracapsular in-situ method remain fewer in the UK than those offering SPAIRE, which is the more widely available of the two techniques in specialist practice here.

Approach selection is anatomy-specific and surgeon-led — but the decision is not one a patient has to enter passively. Two concrete questions are worth raising at a pre-operative assessment: first, how many cases of this specific technique has the surgeon performed independently; and second, if unexpected anatomy requires it, can the incision be extended without repositioning or changing equipment? Learning-curve evidence consistently shows that outcomes with both techniques improve as surgeon case volume grows — for SuperPATH especially, the in-situ femoral preparation demands considerable familiarity before the technique realises its measurable advantages.

Assessing your options for hip arthroplasty

The evidence base for both approaches is still maturing. The ongoing HIPSTER trial — a three-arm RCT comparing robotic-assisted SPAIRE, piriformis-sparing, and standard posterior techniques — is among the studies that may sharpen the picture for SPAIRE in the coming years; equivalent prospective data for SuperPATH in UK practice remains at an earlier stage. For patients working through a treatment decision in the interim, the practical step is a structured surgical assessment: one that considers individual anatomy, the centre's technique experience, and which recovery priorities matter most.

SPAIRE hip replacement is available through Hip Replacement Lincolnshire. The clinical approach to this technique draws on the expertise of Prof Paul Lee, whose published work and research involvement in tendon-sparing arthroplasty inform the evidence base for the approach. Assessment clinics run in Sleaford (NG34) and Grantham (NG31) without GP referral and without NHS-style waiting lists. To book an assessment, visit hipreplacementlincolnshire.co.uk.

1. [1] SuperPATH versus traditional hip replacement in efficacy and safety: an updated systematic review and meta-analysis. (2025). https://doi.org/10.1186/s12891-025-08471-9 https://doi.org/10.1186/s12891-025-08471-9
2. [2] Direct anterior approach vs. SuperPATH vs. conventional approaches in total hip replacement: a network meta-analysis of RCTs. (2021). https://doi.org/10.1016/j.otsr.2021.103058 https://doi.org/10.1016/j.otsr.2021.103058
3. [3] A Standard of Care in Hip Arthroplasty: Routine Use of the Tendon-Sparing SPAIRE Technique with MAKO Robotic Assistance. (2024). https://doi.org/10.1302/1358-992x.2024.16.030 https://doi.org/10.1302/1358-992x.2024.16.030