What the SPAIRE learning curve actually involves

One of the most common misconceptions about the SPAIRE technique is that it places surgeons in unfamiliar territory — it does not. SPAIRE is a modified posterior approach, first described by Kim et al. in 2008, and the posterior route is the one most hip surgeons already know well. The anatomical geography — the planes, the landmarks, the depth of exposure — remains essentially the same.

What changes is intent. In a traditional posterior approach, the piriformis and obturator internus tendons are divided to gain exposure and then repaired at closure. SPAIRE asks the surgeon to reverse that default: instead of cutting and repairing, the goal becomes deliberate identification, careful isolation, and active preservation of those same structures throughout the procedure. That shift — from a 'divide and repair' discipline to a 'preserve from the outset' discipline — is where the learning investment lies.

In practical terms, this demands a finer standard of tissue handling. The surgeon must develop the habit of working around these tendons rather than through them, maintaining awareness of their precise course at every stage of the dissection. That kind of technical re-orientation is not something most surgeons can self-teach from an existing posterior approach habit. It is the sort of refinement that develops through mentored exposure — the model Professor Paul Lee followed during his fellowship training at the Exeter Hip Unit under Professor Timperley, before adopting SPAIRE as his routine practice.

This is why not every posterior approach surgeon automatically offers the SPAIRE variant, and why the spairehips.com registry exists to help patients identify practitioners who have made that specific learning commitment.

How SPAIRE's learning curve differs from the anterior approach

The direct anterior approach (DAA) offers a useful point of comparison. During a surgeon's DAA learning phase, the procedure demands navigation of an entirely different tissue plane — one that most hip surgeons will not have encountered in their earlier training. That unfamiliarity carries documented clinical consequences: intraoperative femoral fracture during canal preparation is a recognised complication of the DAA learning curve, as is lateral femoral cutaneous nerve (LFCN) neurapraxia, which can cause permanent numbness along the outer thigh. These are errors of orientation and plane-finding in new anatomical territory.

SPAIRE's learning curve sits in a different category. Because it builds on a posterior approach that surgeons already understand structurally, the risks during development are not about getting lost in an unfamiliar window. They are concentrated instead in the quality of soft-tissue handling — specifically, whether the surgeon reliably identifies and protects the piriformis and obturator internus rather than inadvertently compromising them.

Neither curve is trivial, and neither should be dismissed. Both require structured training rather than informal self-directed transition. The meaningful distinction for patients is that SPAIRE's formative risks relate to precision and discipline within known anatomy, rather than to plane-orientation errors in unfamiliar ground — a difference with real implications for what supervised training needs to address.

Why precise tissue handling changes what the surgeon can feel and see

Preserving those tendons is not only about protecting the patient after the operation — it changes what the surgeon can feel and decide during it.

When the piriformis and obturator internus remain intact, they maintain the natural tension of the posterior soft-tissue envelope. That physiological tension functions as a live reference: as the surgeon trials components and adjusts implant position, the resistance and balance of the preserved tissues convey moment-to-moment information about leg length and femoral offset. Sever those tissues and that feedback disappears, leaving the surgeon more dependent on imaging references alone to judge alignment.

The obturator internus creates a second distinct mechanical advantage. Its tendon exits the pelvis through the lesser sciatic foramen, wraps around the back of the joint, and inserts on the greater trochanter — a trajectory that places it directly across the posterior femoral head when intact. This creates what is sometimes called the 'strap effect': a dynamic biological tether, something like a natural seatbelt across the back of the joint, that may help resist posterior dislocation in selected patients. Protecting this structure is not incidental; it requires the surgeon to understand its anatomy precisely and work around it with deliberate care throughout the dissection.

Beyond mechanics, the intact tendons house Golgi tendon organs and muscle spindles — sensory receptors that relay the joint's own sense of position to the nervous system. Think of these as the joint's internal orientation signal. Dividing the tendons severs that signal; the joint loses spatial awareness until tissues heal and neural pathways regenerate, a process that takes months.

None of these advantages arise by chance. They depend entirely on complete, undisturbed preservation — which is why the technique rewards trained, deliberate intent rather than approximation.

Why the clinical stakes justify a structured training investment

The dislocation statistics are worth stating plainly, because they reframe the surgeon's training investment as something other than technical perfectionism.

Among patients who experience a dislocation following hip replacement, 57% will go on to dislocate again — it is rarely a single event. Approximately 45.6% of those who dislocate require revision surgery within two years. Revision is a substantially more complex procedure than a primary replacement: it involves greater tissue disruption, longer operating time, extended recovery, and its own set of risks. These figures are not offered to alarm, but to situate what 'posterior stability' actually means in practice for selected patients.

SPAIRE is designed to support stability by keeping the posterior soft-tissue envelope intact from the outset — rather than dividing it and relying on repair to restore function. For suitable candidates, this may help reduce the risk of entering that dislocation cascade at all. But that potential benefit depends on the surgeon completing the preservation work with consistent technical discipline, every time.

Robotic-arm assistance, such as Mako, does play a supporting role: it can deliver sub-millimetre precision for bone resection and implant positioning within a muscle-sparing exposure. That precision matters. What it cannot do is identify and protect the piriformis and obturator internus — the soft-tissue work is surgeon-dependent and cannot be delegated to technology.

For patients, the practical question follows directly: not just whether a surgeon performs the posterior approach, but whether they have specifically trained in the SPAIRE variant.

What a credibly trained SPAIRE surgeon's background looks like

Fellowship-level immersion under an experienced SPAIRE practitioner represents the appropriate entry point — not a self-directed adaptation grafted onto a conventional posterior technique. The procedural re-orientation involved is precise enough that it is best absorbed through supervised cases where the dissection intent, not just the anatomy, can be observed and corrected in real time.

Published engagement with the technique is a second meaningful signal. A surgeon who has contributed a case series, outcome review, or peer-reviewed commentary on SPAIRE has been held accountable for their methods beyond the operating theatre. Peer review introduces scrutiny that routine clinical practice alone does not require, and a publication record indicates the surgeon has reflected critically enough on their results to submit them for external assessment.

High and sustained operating volume matters for a different reason: technique consistency erodes without regular practice. The deliberate tissue-handling that SPAIRE demands is maintained through repetition within a busy NHS or equivalent institutional setting — not preserved indefinitely after an initial training period.

One example of this pathway in practice is Professor Paul Lee's background. He trained in the SPAIRE approach at the Exeter Hip Unit under Professor Timperley, subsequently reviewed and published on its advantages, and then adopted it as his routine practice for total hip replacement — the fellowship-then-publish-then-standardise progression these markers describe. He holds senior consultant posts at the Royal London Hospital (Barts Health) and United Lincolnshire Hospitals NHS Trust, with over 20 years of NHS service. He also founded the UK SPAIRE surgeon registry at spairehips.com, a practical acknowledgement that the variant is not universally available and that patients need a reliable way to identify surgeons who specifically offer it.

How to find a surgeon with genuine SPAIRE training

Knowing what to look for matters only if there is a practical way to act on it. The UK SPAIRE surgeon registry at spairehips.com exists because the technique is not universally offered: a surgeon who performs the standard posterior approach is not automatically in a position to perform the SPAIRE variant. Founded by Professor Paul Lee, the registry identifies practitioners who have specifically adopted this modification — distinguishing them from surgeons with general posterior-approach experience who have not made the deliberate technical transition the technique demands.

At a first consultation, two questions are worth raising directly. First: does the surgeon perform the SPAIRE variant, or the conventional posterior approach? Second: how was that training acquired, and is it their routine practice or an occasional adaptation? A surgeon confident in the technique will answer both without hesitation, and should be able to explain the specific trade-offs for an individual patient's anatomy and recovery circumstances — not offer a single approach as the right answer for everyone.

Suitability for SPAIRE is assessed individually. Anatomy, comorbidities, and implant considerations all influence whether the approach is appropriate for a given patient, and a consultation that addresses those factors honestly is more useful than one focused on a hoped-for outcome.

The practical question the preceding evidence leads to is a direct one: the obturator internus either remains intact to provide that dynamic strap across the posterior femoral head, or it does not. A first consultation is the place to find out whether the surgeon under consideration has trained specifically to make that preservation reliable — and whether this patient's anatomy makes them a suitable candidate for it.