Why surgeon training matters more in some hip replacements than others

Most patients researching hip replacement compare surgical approaches — anterior versus posterior, muscle-sparing versus traditional — and reasonably assume that once they have identified a good technique, results will follow. The reality is more nuanced: within any approach, small differences in how a surgeon executes the procedure produce measurable differences in dislocation risk, recovery speed, and long-term stability.

SPAIRE is a sharper illustration of this principle than most. Its benefits — the dynamic 'strap effect' of the intact obturator internus tendon, and the continuous proprioceptive signals from preserved Golgi tendon organs and muscle spindles — are anatomy-dependent. They exist only if the relevant tendons have been correctly preserved throughout the operation. A surgeon who imprecisely handles those structures may complete a procedure that looks like SPAIRE on paper whilst delivering something closer to a standard posterior approach in biological terms, without the protective mechanisms that distinguish the two.

The clinical stakes of technique quality are worth stating plainly. After dislocation following traditional posterior total hip replacement, 57% of patients experience more than one dislocation event, and 45.6% require complex revision surgery within two years. That cascade begins in the first 90 days post-operation, when severed posterior tissues are still healing. The question for any patient considering SPAIRE, then, is not whether the technique is sound in principle — but whether the surgeon performing it has built the specific skill set to deliver it reliably.

What surgeons actually learn differently with SPAIRE

The shift SPAIRE demands of a posterior-trained hip surgeon is primarily one of discipline rather than orientation. Surgeons who already operate through the posterior approach — by far the most widely used route in the UK — arrive at a SPAIRE procedure knowing the anatomy, the patient positioning, and the theatre layout. What changes is a single governing principle: the tendons at the back of the hip joint that standard technique routinely releases are, in SPAIRE, preserved throughout.

In practice, that means identifying and protecting the piriformis and obturator internus rather than transecting them, then repairing the obturator externus rather than leaving it divided. These are not obscure structures — any posterior-trained surgeon encounters them on every case. The new skill lies in handling them with the precision needed to keep their attachments, blood supply, and mechanoreceptor function intact. That restraint has to become habitual before it becomes reliable, and it is best consolidated through supervised, high-volume exposure rather than self-taught adoption.

Preserved posterior soft tissues also change how the surgeon reads the operative field. With tension maintained across the back of the joint, tactile feedback for intraoperative leg length and femoral offset assessment is enhanced — an internal navigational reference that changes how experienced posterior surgeons interpret what they feel during implantation.

Contrast this with the direct anterior approach (DAA), which requires surgeons to work through an entirely unfamiliar anatomical corridor. The DAA carries a documented risk of intraoperative femoral fractures during canal preparation — a complication pathway that SPAIRE, operating through the established posterior route, does not share. Lateral and SuperPATH approaches each carry their own learning demands; SPAIRE's posterior foundation means the transition is a refinement, not a reorientation — though a demanding one that still requires structured mentored training to execute consistently.

How SPAIRE training is actually transmitted between surgeons

Formal transmission of the technique has a documented lineage. Kim et al. described the underlying Modified Posterior Approach in 2008; Hanly, Sokolowski, and Timperley gave it its current name and published its anatomical rationale in Hip International in 2017. That publication emerged from the Exeter Hip Unit — a centre whose throughput and specialist concentration make it the kind of environment where technically demanding posterior modifications are refined through sustained, supervised volume rather than occasional exposure.

Professor Paul Lee trained in SPAIRE under Professor Timperley at Exeter during fellowship — the structured specialist-to-specialist model through which the technique is most reliably transmitted. After reviewing outcomes and publishing on SPAIRE's advantages in peer-reviewed journals, he adopted it as his routine practice for total hip replacement: not an incidental addition to a broader operating list, but a deliberate, evidence-reviewed commitment.

That pathway matters to patients in a concrete way. A surgeon who absorbed SPAIRE through high-volume mentorship at an originating centre enters independent practice with a different competency baseline than one who adopted the technique from published descriptions alone. The distinction is not merely credentialling — it is reflected in the consistency with which the tendon preservation that generates SPAIRE's clinical advantages is actually achieved on each case.

How SPAIRE training currently reaches UK surgeons without direct Exeter fellowship access has not been systematically published. The practical implication for patients is straightforward: when consulting any surgeon offering a technically demanding posterior approach, asking about their specific training lineage and case volume is a reasonable and informative part of that conversation.

What technology adds during the learning phase

Mako robotic-arm assistance addresses one of the genuine practical constraints of a muscle-sparing exposure: the reduced visual field. By providing sub-millimetre precision for bone resection and implant positioning, the system is described in the evidence as completely negating any visual limitations imposed by the muscle-sparing approach — a meaningful compensatory tool, particularly during earlier cases when the surgeon is still calibrating the modified operative field.

The anatomical side of this equation is distinct from robotics. Keeping the posterior soft tissues intact preserves the surgeon's tactile read of leg length and femoral offset in real time — a reference that standard posterior and DAA approaches lose when those structures are released or avoided. This is not something the robot provides; it is a property of the preserved anatomy that SPAIRE's design makes available.

Together, these two advantages may reduce early-case variability in implant positioning. Neither, however, does anything to ensure the tendons are correctly identified and preserved in the first place. The robot operates on bone; tendon handling remains entirely in the surgeon's hands. For the dislocation-protection mechanisms SPAIRE is designed to deliver to function as intended, the soft-tissue preservation must be executed correctly on every case — and that demands the technical discipline built through structured training, not a robotic workflow.

What the evidence actually shows — and where it goes quiet

The mechanistic case for SPAIRE — the strap effect, continuous proprioceptive feedback, the biomechanical logic of intact tendon preservation — rests on well-established anatomy. The preserved obturator internus tendon's dynamic stabilising function, and the uninterrupted afferent signals provided by intact Golgi tendon organs and muscle spindles, are not speculative; they are grounded in how these structures behave when correctly kept in place. Both mechanisms are technique-dependent: they require the tendons to be accurately identified and preserved, and that execution is down to the operating surgeon on every case.

What the published literature has not provided is the quantitative scaffolding that would let a patient compare one surgeon's early cases against their settled practice. No peer-reviewed source defines a case-volume threshold at which SPAIRE complication rates plateau. No comparative outcome series charts the gap between early-adoption and experienced-practitioner performance. This is a gap in published evidence — not a gap in the technique's anatomical rationale, which stands independently of those missing numbers.

For patients, the practical consequence is straightforward. The literature cannot answer questions about an individual surgeon's case volume or training lineage on their behalf — but those are answerable questions. Asking a prospective SPAIRE surgeon where they trained, under whose supervision, and how many procedures they perform each year is entirely reasonable. A surgeon working within a documented training lineage should be able to respond without hesitation, and the quality of that answer is itself a useful guide.

Choosing a surgeon: what patient suitability and surgeon experience mean together

Patient anatomy shapes every approach decision. SPAIRE is not automatically the right fit for every hip replacement candidate — body habitus, prior surgery on the same hip, bone quality, and the degree of bony deformity all influence which approach gives the operating surgeon the clearest working field and the best conditions for accurate implant placement. A transparent pre-operative consultation should weigh SPAIRE alongside lateral, standard posterior, direct anterior (DAA), and SuperPATH options, setting out the tradeoffs for the individual patient rather than treating any single technique as a foregone conclusion.

Surgeon experience is an equally legitimate input to that conversation. Asking about training background, case volume, and how complications are tracked is appropriate, not intrusive. A surgeon working within a documented training lineage — with direct mentored exposure to the technique rather than self-taught adoption — should be able to respond to those questions with specificity.

Where there is genuine uncertainty about a patient's functional baseline or movement patterns, objective biomechanical assessment adds information that static imaging alone does not provide, and can usefully inform the approach discussion before any surgical plan is finalised.

Professor Paul Lee, whose clinical practice informs the SPAIRE work at this service, sees patients without a GP referral. Hip Replacement Lincolnshire is part of the MSK Doctors group and offers consultant-led assessment at centres in Sleaford and Grantham — earlier access to that conversation, before commitments are made elsewhere, can be the point at which the approach question is most usefully asked.

1. [1] Hip replacement. https://en.wikipedia.org/?curid=1125423 https://en.wikipedia.org/?curid=1125423