What SPAIRE changes — and why it affects who qualifies

SPAIRE is not a different hip replacement — it is a different route to the same operation. The implants, bearing surfaces, and core procedure are identical to any other total hip arthroplasty; what changes is precisely how the surgeon reaches the joint.

The acronym describes what the technique protects: it Saves the Piriformis and obturator Internus, while Repairing the obturator Externus — the one tendon that is divided and subsequently sutured back during the procedure. The piriformis and obturator internus, both short external rotator muscles that play a significant role in rising from a chair, walking, and managing stairs, remain attached throughout surgery.

The technique was developed at the Exeter Hip Unit in 2016 by Professor John Timperley and was adopted by Professor Paul Lee as his standard practice following fellowship training there. It can be used across all routine primary hip replacement indications — osteoarthritis, avascular necrosis, and related conditions that have not responded adequately to conservative management.

For patients and clinicians alike, suitability for SPAIRE is therefore a two-part question. The first is whether hip replacement is appropriate at all. The second — and the main focus of this article — is whether the SPAIRE approach fits a particular patient's anatomy, lifestyle, and risk profile.

Patients who gain the most from this approach

Several groups of patients are particularly well placed to benefit from what SPAIRE preserves — not because the operation itself differs, but because keeping the short external rotators intact has outsized clinical value for certain risk profiles and recovery goals.

Active and sporty patients are the clearest beneficiaries. Intact tendons maintain the proprioceptive feedback the hip relies on to detect position and resist subluxation — an advantage that matters most when patients intend to return to activities such as golf, cycling, or recreational sport. Suitable patients may also have the strict 90-degree flexion and rotation restrictions that follow traditional posterior hip replacement relaxed or removed, reducing daily-life limitations during early recovery.

Patients at statistically higher dislocation risk gain meaningfully from tendon preservation. Evidence indicates that dislocation risk after standard posterior arthroplasty is elevated in patients under 65, women, those with a BMI below 20, and those with a higher comorbidity burden — with 57% of those who dislocate doing so again, and 45.6% requiring revision surgery within two years. The mechanical stability that the intact obturator internus provides is designed to address that risk from the outset.

Those planning same-day or next-day discharge also align well with the approach. A rapid recovery pathway integrating technique, implant choice, and early mobilisation can support discharge within 24 hours for appropriately selected patients. In a prospective case series of 35 SPAIRE arthroplasties, mean return to orthotic-assisted ambulation was 1.5 days and mean Harris Hip Score at two months was 83.16. That series is small and not a randomised controlled trial, so findings are best read as indicative rather than definitive — but they sit consistently with the physiological rationale for preserved muscle function. This evidence caveat applies equally to the clinical detail discussed in subsequent sections.

The technique also extends to anatomically complex cases: severe hip dysplasia, slipped capital femoral epiphysis (SCFE), and Perthes disease are all within its documented scope, widening applicability beyond straightforward primary osteoarthritis.

Finally, patients motivated to avoid prolonged movement restrictions are strong candidates, provided they meet standard total hip arthroplasty criteria and their anatomy allows the muscles to be reached in their natural planes.

Why preserved tendons translate to stability

Two distinct mechanisms explain why keeping the short external rotators intact translates into measurable joint stability — one mechanical, one neurological.

The mechanical contribution comes from the obturator internus tendon's anatomy. In the SPAIRE approach, this tendon remains undivided and passes directly over the posterior surface of the femoral head at or close to the joint's true centre of rotation. The result is a biological tether — referred to by the technique's developers as the 'strap effect' — that actively resists posterior subluxation. The resistance is pronounced: surgeons must use a bone hook to dislocate the hip during the procedure itself because the intact tendon holds the joint reduced with considerable force.

The neurological contribution operates through a separate pathway. Embedded within the short external rotators are Golgi tendon organs and muscle spindles — mechanoreceptors that transmit continuous afferent signals to the central nervous system about joint position and load. When a standard posterior approach divides these tendons, those signals are interrupted. The joint becomes, in effect, neurologically blind to its own position until scar tissue matures and neural pathways partially regenerate — the period during which strict movement precautions are enforced to compensate for that loss.

In SPAIRE, both lines of protection remain active from the day of surgery. The physical strap resists unwanted posterior movement; the intact sensory apparatus feeds back real-time positional data. Together, these mechanisms provide the physiological basis for the low dislocation rates observed in published series and the clinical rationale for relaxing the movement restrictions that standard posterior approaches require.

When SPAIRE is not the right choice

SPAIRE may not be appropriate in a number of situations — some shared with any total hip arthroplasty, and one specific to this approach.

Absolute contraindications are the same as for standard THA: active local or systemic infection (including bacteraemia) rules out elective surgery until it is fully resolved, and severe cognitive or neuromuscular impairment that prevents active rehabilitation makes early mobilisation — central to the recovery pathway — unachievable.

Relative contraindications affect the risk–benefit balance rather than excluding a patient outright. Morbid obesity (BMI above 40) raises wound-healing and deep infection risk to a level that may outweigh the benefits of any arthroplasty approach. Severe osteoporosis with insufficient bone density to anchor the femoral stem is a structural barrier regardless of how the joint is accessed. Uncontrolled cardiovascular or pulmonary disease affects fitness for anaesthesia and early mobilisation rather than the surgical route itself.

The SPAIRE-specific limitation concerns soft-tissue anatomy. The technique depends on the short external rotators being accessible in their natural planes. Where extensive previous hip surgery has scarred or repositioned those tissues, the muscles cannot be preserved because their anatomical positions are already disrupted — the core advantage of the approach disappears along with its premise. For these patients, a different surgical route is generally more appropriate.

Surgeon availability is a practical factor that sits alongside clinical ones. SPAIRE requires specific training in this modification of the posterior approach, and not every hip surgeon has completed it — the technique's benefits are inseparable from the surgeon's familiarity with it.

For most patients who meet standard THA criteria and have not had extensive prior hip surgery, these exclusions are the exception. Where they do apply, the relevant question is not whether hip replacement is warranted — often it remains so — but which approach best suits the individual's anatomy, history, and recovery goals.

How SPAIRE compares to other approaches

Four main surgical routes are used for total hip arthroplasty in the UK, each with documented advantages and trade-offs.

Standard posterior approach is the most widely performed technique and SPAIRE's direct predecessor. The surgeon accesses the joint from the rear, dividing the short external rotators for exposure. This produces reliable results but carries two linked limitations: a heightened dislocation risk during healing — managed with strict 90-degree flexion and rotation precautions for up to 12 weeks — and a period of impaired proprioception while severed mechanoreceptors regenerate. SPAIRE was developed specifically to address those two limitations within the same posterior corridor.

Anterior approach (DAA) goes in from the front of the hip, working between muscle planes rather than through them, and avoiding posterior structures entirely. Early functional recovery is often cited as an advantage. Equally documented trade-offs include the need for a specialist operating table, proximity of the lateral femoral cutaneous nerve to the incision with a recognised risk of traction injury, and more limited acetabular visualisation in patients with higher BMI or certain body proportions.

Lateral (Hardinge) approach enters from the side, avoiding the posterior dislocation risk and the associated movement precautions. The trade-off is partial detachment of the gluteus medius. Where that repair does not heal fully, a Trendelenburg gait — a characteristic hip-drop when walking — can follow.

SuperPATH is a minimally invasive posterior technique that preserves the joint capsule and avoids the standard posterior approach's tendon division. It shares common ground with SPAIRE in prioritising soft-tissue preservation from the rear, but uses a different anatomical window and tissue-preservation logic.

No single approach is universally the right choice. Surgeon training, patient anatomy, BMI, bone stock, and the underlying hip pathology all influence which route is appropriate — a question best answered through a consultant-led assessment that weighs each of those factors individually.

Getting a formal suitability assessment

Broad suitability is only the starting point. Even patients who recognise themselves clearly in the profiles described above — active, broadly normal weight, no extensive prior hip surgery — still need a formal assessment to translate that general fit into a specific surgical plan.

That assessment covers hip joint imaging (X-ray as standard, MRI where bone stock or soft-tissue detail warrants it), current BMI, comorbidity and medication history, prior surgical history, and the patient's own functional goals. Together, these determine not only whether hip replacement is appropriate but which approach, implant, and recovery pathway best matches the individual.

Patients who find two or more of the earlier profiles apply to them — an active lifestyle, identifiable dislocation-risk factors, a wish to avoid strict postoperative precautions — are well placed to raise SPAIRE specifically in that conversation and to ask what the approach would mean for their particular anatomy and goals.

Prof Paul Lee, whose clinical approach informs this site's discussion of the technique, carries out these assessments at Hip Replacement Lincolnshire — no GP referral is needed. Clinics are available at Sleaford (NG34) and Grantham (NG31); appointments can be booked at hipreplacementlincolnshire.co.uk.