Two innovations, two anatomical layers

If a surgeon has mentioned both 'SPAIRE' and 'bikini incision' in the same conversation, the natural question is whether these are two names for the same thing — or two separate decisions. They are separate, and that distinction matters.

SPAIRE hip replacement works deep inside the joint: it is a modified posterior approach that keeps the small stabilising tendons at the back of the hip — the piriformis and obturator internus — attached to bone throughout surgery, rather than releasing and reattaching them. The bikini incision works at the surface: it repositions the skin cut along the body's natural crease lines so the resulting scar sits in a discreet, low-visibility location.

Neither technique changes the hip implant itself. Both change only how the surgeon reaches the joint — one at the tendon layer, one at the skin layer.

Because the two innovations act at different anatomical depths, they are additive. What each layer contributes — and why the combination represents a more complete approach to tissue protection — is what this article sets out to explain.

What SPAIRE preserves beneath the skin

The acronym itself maps to the anatomy: Save Piriformis And Internus, Repair Externus. The piriformis and obturator internus are two of the short external rotator tendons clustered at the back of the hip joint. Their mechanical integrity after surgery is closely linked to how stable the hip feels in the early weeks of recovery.

In a conventional posterior hip replacement, accessing the joint requires releasing these tendons from their bony attachments. The access is effective, but the tendons are temporarily disconnected from bone. Surgeons have traditionally compensated by imposing strict post-operative movement restrictions — rules about bending, crossing the legs, or rotating the foot inward — designed to protect the repair while it heals and to reduce the risk of dislocation during that vulnerable period.

The SPAIRE technique, formalised by Hanly, Sokolowski and Timperley in Hip International in 2017, was developed to avoid that release-and-repair cycle entirely. By keeping the piriformis and obturator internus attached to bone throughout the procedure, the surgeon maintains a continuous tendon sleeve around the posterior hip. That preserved sleeve is designed to support earlier joint stability, and for suitable patients some of the strict early movement precautions associated with conventional posterior surgery may be able to be relaxed — though individual restrictions remain a clinical decision based on the specifics of each case.

Professor Paul Lee trained in the SPAIRE approach under Professor Timperley at the Exeter Hip Unit, the centre where the technique was formalised, and that provenance informs the clinical approach taken at Lincolnshire Hip.

All of this work occurs entirely beneath the skin. The position and appearance of the incision are unaffected by the SPAIRE technique — those are determined by separate decisions made at the surface level.

What the bikini incision changes at the surface

Along the natural crease where the thigh meets the groin, most people can feel a horizontal fold in the skin. That fold is precisely where the bikini incision is sited.

Skin has a preferred direction of tension, described anatomically as Langer's lines. Cutting parallel to those lines is associated with neater healing and improved scar cosmesis; cutting across them tends to produce wider, more conspicuous results. Rather than using the longitudinal cut of a standard direct anterior approach, the bikini incision runs horizontally along the natural crease, following the skin's own tension lines from the outset.

The scar that results typically sits lower and less prominently than a conventional surgical incision in the same region. In many female patients, it falls within the bikini line and may be concealed by swimwear — hence the name. Scar appearance varies between individuals, and 'positioned to be less visible' is a more accurate framing than any guarantee of invisibility.

The incision orientation also influences what lies immediately beneath. Approaching from a lower, more transverse angle limits how far the tensor fascia lata needs to be disturbed to reach the hip joint, and allows the anteromedial joint capsule to be preserved. The associated reduction in intraoperative blood loss and the conditions for early mobilisation arise from the access strategy that this incision orientation makes possible — they are properties of the whole approach, not of the skin cut considered in isolation. In both cases, the joint implant itself is unchanged.

What the combination achieves that either approach alone does not

The question of what the combination adds is answered by geography. SPAIRE operates entirely at depth — tendons, joint capsule, the stabilising structures behind the hip. The bikini incision operates entirely at the surface — skin placement, scar orientation, wound healing. Because neither technique trespasses on the other's anatomical territory, their benefits are additive rather than overlapping.

That non-overlap is the clinical argument. A SPAIRE procedure alone leaves the skin incision undefined: the surgeon has preserved the posterior tendon sleeve, but the position and appearance of the wound are determined by a separate decision made independently of anything happening deeper. A bikini incision alone addresses the scar but contributes nothing to tendon integrity at the back of the hip. Combining them closes that gap — one technique handling the deep layer, the other the surface, a tissue-sparing rationale applied consistently from the epidermis inward.

The functional gains — earlier joint stability, the possible relaxation of certain movement restrictions in suitable patients — originate in the deep work of SPAIRE. The aesthetic and wound-healing gains — a low-visibility scar, alignment with skin tension lines, the conditions for early discharge — originate in the surface work of the bikini incision. The two sets of benefits are distinct in origin and distinct in character; one does not substitute for the other.

What the combined approach currently lacks is its own outcomes literature. Published biomechanical and anatomical data support each technique individually, but head-to-head trial data comparing bikini-SPAIRE against SPAIRE alone — on scar satisfaction scores, wound complication rates, or patient-reported cosmetic outcomes — have not yet appeared in large published series. Patients weighing this option should hold that gap in mind when discussing suitability at consultation.

Which patients are suitable — and how the decision is made

Before patient selection can be discussed honestly, one apparent tension in this article deserves a direct answer. SPAIRE is a posterior approach — the surgeon accesses the hip from behind. The bikini incision is most commonly associated with direct anterior access — from the front. Readers who have followed the earlier sections carefully may wonder how techniques on opposite sides of the body can sensibly be described as working together.

The resolution lies in the principle rather than the label. A bikini-style incision is defined by how the skin is cut — horizontal, aligned with natural skin tension lines, positioned along the body's own crease geography rather than running longitudinally for the surgeon's convenience. That orienting principle is not exclusive to anterior access. Applied at a posterior entry point, it means the skin cut follows skin creases in that region rather than running vertically across them, repositioning the resulting scar to a lower and less conspicuous site. The deep muscle-and-tendon-sparing work of SPAIRE and the surface cosmetic work of crease-aligned skin placement then proceed from the same posterior entry point. Understanding that distinction makes the combination coherent rather than contradictory.

Suitability for this approach is assessed individually, and not every patient is an appropriate candidate. Body habitus, hip geometry, bone anatomy, and any prior surgery to the region all influence whether a muscle-and-tendon-sparing posterior access is feasible. Where anatomy does not permit it, other approaches — a lateral technique, standard posterior, direct anterior DAA, or SuperPATH — each remain valid options, with their own trade-offs in nerve risk, intraoperative visualisation, and recovery profile. None is universally superior; each suits a different clinical picture.

At Lincolnshire Hip, approach selection follows a formal consultant assessment. Prof Paul Lee reviews each patient's imaging, anatomy, and clinical priorities before recommending a route — so that the decision reflects what is achievable and appropriate for that individual rather than a fixed preference.

Recovery, mobilisation, and what patients at Lincolnshire Hip can expect

Recovery after a combined bikini-SPAIRE procedure follows the same broad arc as any hip replacement — physiotherapy, a phased return to daily activities, and a gradual resumption of movement — but two features of this approach may shape its character.

The SPAIRE technique's most tangible recovery implication is the potential relaxation of some movement restrictions in suitable patients. In a conventional posterior approach, reattached tendons heal under tension, and early movement limits partly exist to protect those repairs. Where the tendons were never released, that rationale weakens — and in appropriate cases, a consultant may ease some of the usual early rules. Whether this applies to any individual depends on anatomy and the surgeon's intraoperative judgement; it should not be assumed in advance of a clinical assessment.

At the surface, the bikini incision's alignment with natural skin tension lines continues to support recovery after discharge. Wounds placed parallel to skin creases tend to heal with less tension on the edges, which may reduce visible scar widening in the weeks that follow.

Standard hip replacement guidance — physiotherapy, driving, stairs, and gradual return to activity — applies regardless of approach; individual progress, not a fixed schedule, determines timing.

Lincolnshire Hip is part of the MSK Doctors group and accepts patients without referral for hip assessment, with access points in Sleaford and Grantham. The most useful question to bring to that first consultation is not only which implant will be used, but how the surgeon accesses the joint — and whether those decisions, at depth and at the surface, have each been matched to the patient's own anatomy.