SPAIRE Hip Replacement Benefits, Limitations, and Who It Suits

What SPAIRE actually does differently at the hip joint

Every standard posterior hip replacement involves dividing a group of small but mechanically important tendons at the back of the joint — the short external rotators — to gain access to the acetabulum and femoral head. Of those tendons, two do particular work: the piriformis and the obturator internus. In a conventional posterior approach, both are cut and left to heal over several weeks, creating a vulnerability window during which the posterior capsule cannot fully resist dislocation.

SPAIRE changes that calculus by preserving piriformis and obturator internus entirely. Only the obturator externus tendon is divided, and it is repaired at the end of the procedure. The preserved obturator internus tendon follows an anatomically distinctive path: it wraps around the lesser sciatic notch and then passes directly over the posterior surface of the femoral head. This trajectory creates what is described as a 'strap effect' — a biological tether that provides passive and dynamic resistance to posterior dislocation even in the immediate postoperative period, before any healing has occurred.

Beyond mechanical stability, the intact tendons retain their sensory nerve endings — Golgi tendon organs and muscle spindles — that relay continuous proprioceptive signals to the nervous system. Severed tissue cannot provide that feedback until slow neural regeneration takes place.

Developed at the Exeter Hip Unit and published in 2018, SPAIRE is a refinement of the posterior approach rather than a new access route. It can be applied to total hip arthroplasty and, in its HemiSPAIRE form, to hemiarthroplasty for fractured neck of femur.

The strongest documented advantages

The most immediately practical benefit for patients is the elimination of post-operative hip precautions. Because the obturator internus tendon remains intact and provides immediate passive stability via the strap effect, there is no need for the 90-degree flexion restrictions or crossed-leg prohibitions that follow traditional posterior surgery. Those restrictions exist because severed rotators take weeks to heal — a window during which, once dislocation occurs, published data suggest 57% of patients experience further events and 45.6% ultimately require complex revision surgery. SPAIRE removes that window entirely from the outset.

The original 2018 Bone & Joint series — comparing 42 consecutive SPAIRE cases with 86 traditional posterior cases — provides the earliest formal clinical evidence. There were no statistically significant differences in blood loss, length of stay, or complication rates; the technique added a mean of eight minutes to operative time. SPAIRE patients reported higher satisfaction at six weeks and showed less measured limb length discrepancy. A 2024 Indian prospective series of 35 patients recorded a mean Harris Hip Score of 83.16 at two months and a mean time to assisted ambulation of 1.5 days; one dislocation occurred at three months following a fall.

Early data are encouraging, though large head-to-head randomised trials — including the NIHR-funded HIPSTER study — are still ongoing. These series establish that SPAIRE is safe and produces good early functional outcomes; they do not yet constitute the level of evidence that only long-term RCTs can provide.

A further proposed advantage is proprioceptive continuity: because the short external rotators are preserved, their sensory nerve endings remain functional from day one, potentially providing continuous neurological feedback during recovery. The mechanism is anatomically well-reasoned, but it has not been separately measured or quantified in published outcome studies and should be understood as plausible rather than formally proven.

How SPAIRE compares to other hip replacement approaches

Approach selection is one of the more consequential decisions in hip arthroplasty, and no single route suits every patient equally.

Against the standard posterior approach

The standard posterior approach cuts the same tendons SPAIRE retains, requiring weeks of restricted movement while those tissues heal. During that period, dislocation carries serious downstream consequences — as noted in s2. By contrast, the intact posterior soft-tissue envelope in SPAIRE means stability is present from the moment the patient wakes up, without mandating movement restrictions.

Against the direct anterior approach (DAA)

The DAA enters the hip from the front, theoretically avoiding the posterior capsule altogether. It may offer marginally faster pain relief in the first six to twelve weeks, though this early advantage appears modest and time-limited in published comparisons. The tradeoffs are material: DAA requires a specialised traction table and intraoperative fluoroscopy; it also risks the lateral femoral cutaneous nerve — a structure not near the SPAIRE incision — which, if injured, causes permanent numbness along the outer thigh. The posterior incision used in SPAIRE can also be extended readily if fracture, dysplasia, or unexpected anatomy demands it; the DAA corridor offers less flexibility.

Against the lateral (Hardinge) approach

The lateral approach remains widely available through NHS centres and provides broad acetabular exposure. Its limitation is proximity to the superior gluteal nerve and the abductor mechanism; damage here can cause a persistent limp. SPAIRE does not enter that territory, though availability varies — the lateral approach can be offered by a much larger pool of NHS surgeons than SPAIRE currently.

Against SuperPATH and mini-posterior variants

SuperPATH and mini-posterior techniques share the goal of minimising soft-tissue disruption but use different tissue corridors and implant delivery strategies. Direct comparative data with SPAIRE have not been published, so meaningful efficacy comparisons between them remain premature.

The right approach depends on patient anatomy, case complexity, and surgeon training — which makes individual assessment, rather than approach preference alone, the meaningful starting point.

Who is a good candidate — and when SPAIRE may not be the right fit

For most patients undergoing primary total hip arthroplasty or hemiarthroplasty, SPAIRE is a viable option — it is not a technique reserved for a narrow anatomical profile or unusually straightforward cases. The more relevant question is whether a surgeon with specific muscle-sparing posterior approach experience is involved.

That said, three anatomical characteristics make the procedure technically more demanding. Patients with small hip anatomy, reduced femoral offset, or a fixed external rotation deformity present the greatest intraoperative challenge; the originating surgeon at the Exeter Hip Unit explicitly identifies these as the hardest cases in the technique. In such situations, sub-optimal visualisation of the posterior acetabulum can complicate accurate implant placement. High-volume SPAIRE surgeons, including those who have adopted it as a standard of care across more than 1,000 consecutive cases, typically address this with Mako robotic assistance — which provides sub-millimetre implant positioning precision independent of the degree of soft-tissue exposure. Robotic assistance extends the technique's practical range in complex anatomy rather than being a prerequisite for straightforward cases.

Operative time averages approximately eight minutes longer than traditional posterior hip replacement. For most patients this is inconsequential, but it is worth factoring in for anyone with significant anaesthetic risk.

Availability is a practical constraint: SPAIRE requires specific training and is not offered by all hip arthroplasty surgeons. Individual suitability is ultimately a matter for consultant assessment — anatomy, offset, bone quality, and case complexity all inform whether the approach is the right fit for a given patient.

What the current evidence shows — and what is still being established

Published evidence for SPAIRE currently rests on case series and comparative cohort studies — most notably the original 2018 Bone & Joint series of 42 SPAIRE versus 86 traditional posterior cases, and a 2024 prospective Indian series of 35 patients. These confirm early safety and functional recovery, but no randomised controlled trial has yet reported head-to-head outcomes comparing SPAIRE directly against the standard posterior approach or the direct anterior approach for total hip arthroplasty.

One RCT does exist in an adjacent area: a 158-patient trial comparing SPAIRE against the DAA in hemiarthroplasty found equivalent periprosthetic bone mineral density changes at three and twelve months. This is a reassuring finding — it indicates no elevated periprosthetic fracture risk between the two approaches — though bone density is a secondary measure, not the clinical outcome most patients ask about.

The study that will matter most is the NIHR-funded HIPSTER trial: a single-centre, double-blinded, three-arm RCT comparing SPAIRE, a piriformis-sparing approach, and the standard posterior technique in total hip arthroplasty. It was actively recruiting in 2024. When results are published, they will constitute the highest-quality comparative evidence yet available.

Long-term implant survivorship data specific to SPAIRE — the ten-plus-year figures that inform how a prosthesis holds up over a lifetime — do not yet exist. Hip arthroplasty broadly has a strong track record, with around 58% of total hip replacements estimated to last 25 years, but those figures derive from the established approaches and cannot be applied directly to SPAIRE. For a technique first performed in 2016, this is a straightforward consequence of age rather than a signal of concern — the data simply have not had time to accumulate.

Getting assessed for SPAIRE at Hip Replacement Lincolnshire

For any patient weighing up SPAIRE, the practical next step is a structured hip arthroplasty assessment — covering clinical examination, imaging review, and a frank discussion of anatomy, activity demands, and what the patient wants from surgery. Approach selection, including whether SPAIRE is appropriate, forms part of that surgical planning conversation rather than a separate decision.

At Hip Replacement Lincolnshire, assessments are informed by Prof Paul Lee's clinical approach to muscle-sparing posterior arthroplasty. Where relevant, objective gait analysis through MAI Motion® can support pre- and post-operative functional monitoring — useful for tracking recovery after a technique that preserves soft-tissue continuity from day one.

Patients do not need a GP referral. Assessment appointments are available at Sleaford (NG34) and Grantham (NG31), and the service accepts patients from across the wider non-London catchment without NHS-style waiting lists. Further information and bookings are at hipreplacementlincolnshire.co.uk.

1. [1] 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
2. [2] THE SPAIRE TECHNIQUE ALLOWS HIP ARTHROPLASTY WITH DIVISION OF ONLY THE OBTURATOR EXTERNUS TENDON. (2018).