Why both techniques exist — and what they share

For most people weighing up hip replacement options, the first question is practical: SuperPATH and SPAIRE both get mentioned as gentler alternatives to standard surgery — so what actually separates them, and does the difference matter?

Both are muscle-sparing modifications of the posterior approach to total hip arthroplasty (THA), the surgical corridor that runs along the back of the hip joint. That route has long been surgeons' most common choice because it offers a clear view of the joint and reliable access to both the acetabulum and femoral head. Its historic drawback, however, was that accessing the joint traditionally required cutting through the short external rotator tendons — the small but important muscles that stabilise the hip and control rotation. Severing them raised the risk of early dislocation and meant patients had to follow strict movement restrictions for up to 90 days afterwards: no bending the hip past 90°, no crossing the legs, no sleeping on the affected side.

SuperPATH and SPAIRE were each developed specifically to address that problem. By protecting the posterior soft tissues rather than cutting through them, both techniques remove the mechanical justification for those restrictions and support faster, more natural early recovery. Neither is a branded implant system — both are surgical methods, and outcomes depend directly on the operating surgeon's training, volume, and case experience.

What each technique actually does differently

The clearest way to understand the difference is through what each technique chooses not to disturb.

SPAIRE — Saves Piriformis And Internus, Repair of Externus — approaches the hip from behind, opening the posterior capsule to access the joint. The piriformis and obturator internus tendons are left entirely intact throughout, working around them rather than through them. The obturator externus is detached briefly to improve access, then repaired meticulously before closure. Importantly, the hip joint is still dislocated during the operation to allow the femoral head to be removed and the new components positioned — the distinction from standard posterior surgery lies not in whether the hip moves, but in which tendons are protected at every step. This is the approach originally described as the Modified Posterior Approach by Kim et al. in 2008.

SuperPATH takes a more radical step along the same trajectory. The surgeon develops a working window in the plane between the gluteus minimus and piriformis, entirely above the hip capsule. The capsule is never opened, and the femoral head is removed in situ — in sections, without ever dislocating the hip at all. The incision can be as small as 7–8 cm, and the procedure relies on instruments specifically designed to operate within this narrow supracapsular corridor.

That structural difference has a direct bearing on intraoperative safety. Because SPAIRE follows a recognisable posterior anatomical plane, a surgeon can convert to a full conventional posterior exposure immediately should an unexpected complication arise — unusual anatomy, an instrument fracture, or bleeding that needs direct control. SuperPATH's supracapsular window is considerably harder to extend under those same circumstances, which places greater demands on a surgeon's specific and sustained experience with that particular technique before applying it to more complex cases.

Dislocation risk — how each technique protects the hip

After standard posterior hip replacement, dislocation sets off a troubling chain: around 57% of patients who experience one episode will go on to have more, and 45.6% of those who dislocate require revision surgery within two years. Both SuperPATH and SPAIRE are designed with those numbers in mind, though each addresses the risk through a different mechanism.

SPAIRE's protection is structural and immediate. The preserved obturator internus tendon runs directly across the back of the femoral head, acting rather like a natural seatbelt — it is under physiological tension from the moment the patient wakes, resisting any force that would push the new joint out of position. This 'strap effect' is not a compensatory mechanism created by the surgery; it is the native anatomy, undisturbed and functional. The intact mechanoreceptors within the preserved tendons also continue sending position signals to the brain in real time, giving the nervous system an immediate sense of where the joint sits — something a conventionally operated hip cannot offer until scar tissue matures.

SuperPATH approaches the same problem from the opposite direction. If the posterior soft-tissue structures are never divided — because the hip is never dislocated during surgery at all — there is nothing to heal and nothing to protect during recovery. A published 344-case series reported zero dislocations and zero infections with this approach. It is worth being transparent about the evidence level here: this is a single-surgeon series, not a randomised controlled trial, so the result reflects one centre's experience rather than a pooled evidence base.

Together, the two techniques address dislocation risk through complementary logic — SPAIRE by preserving what stabilises the joint, SuperPATH by ensuring it is never destabilised in the first place.

Recovery — what patients can expect from each approach

Removing the strict movement restrictions that follow standard posterior surgery is the most immediately practical difference for patients recovering from either technique. Neither SPAIRE nor SuperPATH leaves the posterior soft-tissue envelope in a disrupted state that needs protecting during healing, so neither requires the familiar prohibitions — no bending beyond 90°, no crossing the legs — that can dominate the first three months after a conventional posterior hip replacement.

Both approaches target mobilisation on the day of surgery or the following day. The strongest quantitative recovery data comes from the SuperPATH literature: across meta-analyses pooling multiple randomised controlled trials, patients consistently experienced shorter incisions (approximately 4.84 cm less than the conventional posterior approach), a clinically meaningful reduction in pain at day seven (VAS score approximately 1.4 points lower), and Harris Hip Score improvements of around 10 points at one week compared with standard surgery. Earlier return to daily activity and a shorter hospital stay are reported across three separate meta-analyses, reflecting an early-discharge philosophy that the supracapsular technique was designed around.

For SPAIRE, the recovery aims are directly comparable — same-day walking, no precautions, earlier return to a natural gait — but the evidence sits primarily at the mechanistic level rather than in large head-to-head randomised trials. The clinical rationale is well-established: intact proprioceptive pathways and an undisturbed posterior soft-tissue restraint mean the neuromuscular system begins re-patterning immediately rather than waiting for scar tissue to mature. The large-scale comparative data accumulating this recovery trajectory is still in progress.

Both techniques reflect the understanding that a hip which starts moving naturally from day one tends to recover more smoothly — and that the most disruptive element of traditional posterior recovery, the precautions themselves, can be safely removed when the posterior structures are protected rather than sacrificed.

What the evidence actually shows — and where gaps remain

For SuperPATH, the volume of comparative trial data is notable by surgical-technique standards. Three independent systematic reviews and meta-analyses — including one pooling 36 randomised controlled trials and another covering 12 RCTs across 726 patients — converge on the same picture: shorter incisions, shorter hospital stays, less early pain, and better early function scores than conventional posterior THA. That consistency across independent analyses, rather than any single dramatic finding, is what gives the evidence genuine weight.

Two trade-offs surface with equal consistency across those reviews. Operative time for SuperPATH is reliably longer than for the conventional posterior approach — a direct consequence of the technically demanding supracapsular working window and the learning curve associated with working through a constrained portal without dislocating the hip. Prosthetic cup positioning accuracy also appears marginally lower in SuperPATH groups in the comparative data, though postoperative complication rates between the two approaches are otherwise equivalent. Patients who hear from their surgical team about longer theatre times are hearing something the published evidence supports.

SPAIRE's evidence occupies a different tier — not because the clinical rationale is weak, but because large-scale meta-analytic comparison data specific to SPAIRE is not available from the retrieved literature. The anatomical and biomechanical case for tendon preservation is well-grounded; how that translates into population-level outcome statistics relative to conventional or alternative approaches remains an area where the evidence is still developing.

Both techniques also carry a meaningful surgeon learning curve and are not universally available across NHS or independent centres. The operating surgeon's depth of experience with the specific approach is a genuine influence on outcomes — a practical consideration worth raising during any pre-operative assessment.

Which approach suits which patient — and how to find out

The question most patients arrive with — 'which technique is better?' — is the wrong one. The question that actually shapes a surgical plan is: 'which approach suits my anatomy, my risk profile, and the training volume of the surgeon assessing me?'

Neither SPAIRE nor SuperPATH is the universal right answer. SPAIRE's posterior foundation makes it straightforwardly extensible: if intraoperative anatomy proves more complex than pre-operative imaging suggested, the surgeon can convert immediately to a full conventional posterior exposure without any compromise mid-case. SuperPATH's constrained supracapsular window does not offer that flexibility — and removing the femoral head in sections through a small portal places particular demands on surgical experience, meaning outcomes are closely tied to the operating team's training history.

Body habitus, hip morphology, implant requirements, co-morbidities, and a surgeon's specific depth of practice with a given technique all enter the equation. Determining which combination is appropriate for a particular patient is the work of a structured clinical assessment, not a decision checklist — and those questions belong in a consultation room rather than resolved by reading alone.

Professor Paul Lee, whose clinical perspective informs the SPAIRE approach described throughout this article, practises it as his routine posterior approach and sees patients through Hip Replacement Lincolnshire in Sleaford and Grantham, without the need for a GP referral.

To arrange a consultant-led assessment, visit hipreplacementlincolnshire.co.uk.