The short answer: learning curve, not clinical inferiority

Most surgeons who perform hip replacement do not use the direct anterior approach (DAA) — not because it is unsafe or ineffective, but because becoming genuinely proficient at it demands roughly 100 cases, a threshold that takes the average orthopaedic surgeon four or more years to reach. During that period, patients operated on early in a surgeon's learning curve face a measurably elevated risk of revision surgery. For surgeons who already achieve reliable results through a well-practised posterior route, that transition cost is hard to justify.

The second part of the answer is equally important: once a patient is twelve months post-operative, outcomes between approaches are broadly equivalent. Pain, function, and implant survival are similar regardless of which route the surgeon took. The anterior approach does offer a genuine early-recovery advantage — less discomfort and faster return to daily activities in the first four to six weeks — but that window of benefit does not translate into a meaningful long-term difference.

Four overlapping reasons explain the full picture: a steep and volume-intensive learning curve; practical barriers around theatre time, equipment, and implant choice; limits on which patients are suitable candidates; and the absence of any compelling long-term outcome advantage. Each of these is worth examining in turn.

The learning curve: what the evidence actually shows

The risk is not evenly distributed across those hundred cases. According to a Dutch registry analysis of 15,875 total hip arthroplasties (Peters 2022), the curve breaks into identifiable phases: revision risk runs 64% above the surgeon's eventual steady-state rate during the first 50 cases, then remains roughly 30% elevated between cases 51 and 100, before settling into a stable plateau from case 100 onwards. That gradient matters ethically as much as practically — the earliest patients in a learning cohort shoulder disproportionately more risk than those treated once proficiency is established.

For established surgeons, the career arithmetic compounds the problem. A 2019 survey of AAHKS members found that surgeons who had adopted the DAA had practised, on average, 17.0 years compared with 20.9 years for non-adopters (Patel et al., 2019). The gap is telling: surgeons earlier in their careers are building their practice around DAA from the outset, whereas those with decades of reliable posterior outcomes are being asked to accept a step backwards in patient safety — temporarily, but measurably — before arriving at equivalent results.

This is a structural tension rather than a character flaw in any individual surgeon. A busy specialist unit with high annual hip volumes can absorb a learning curve within a year or two and distribute early-case risk across a larger institutional safety net. For a lower-volume general orthopaedic surgeon, the same curve stretches across years with no comparable buffer. The evidence does not suggest DAA surgeons are reckless; it suggests the procedure's demands are mismatched with the workload patterns of most orthopaedic practices.

Theatre logistics and technical demands of the anterior approach

Beyond any individual surgeon's aptitude, the anterior approach imposes a set of system-level demands that many NHS units are simply not equipped to meet. Performing DAA reliably typically requires a specialised orthopaedic traction table, intraoperative fluoroscopy — used by around 56.7% of DAA surgeons to verify implant alignment — and, in some centres, robotic assistance (employed by roughly 12% of DAA practitioners). Each represents a capital outlay that must be justified against throughput, competing departmental priorities, and procurement cycles that move slowly in any large health system.

Theatre time adds a further institutional pressure. A multicentre randomised controlled trial reported mean operative times of 69.9 minutes for DAA versus 45.7 minutes for the posterior approach; a 2025 observational study found an even wider gap, at 117 versus 79 minutes. In a system where operating lists are tightly scheduled, a consistent 30–40 minute excess per case has real consequences for capacity.

Implant choice is also more constrained from the anterior direction. Because femoral exposure is more technically demanding via this route, surgeons often rely on shorter stem designs whose long-term registry performance is less established than that of standard stems used posteriorly.

The combined effect of these factors is visible in uptake figures: fewer than 1% of hip replacements in the UK use the anterior approach. At the 2025 Anterior Hip Foundation meeting, UK surgeons identified limited NHS training pathways, equipment investment costs, and the professional exposure of deviating from established practice in a registry-scrutinised environment as the primary structural barriers — none of which reflects individual surgical unwillingness.

Patient suitability: anterior hip replacement is not for everyone

Anatomy and body habitus impose real limits on who can safely receive an anterior hip replacement, and those limits apply to a meaningful share of patients who might otherwise be interested in the approach.

The surgical corridor used in DAA runs between the tensor fasciae latae and the sartorius, nowhere near the gluteus medius and minimus tendons at the back of the hip. This matters because abductor tendon tears — though not common — do occur, and surgeons using posterior or lateral approaches can identify and address them during the same procedure. Through the anterior route, those tendons cannot be seen, assessed, or repaired. Patients in whom abductor pathology is suspected are therefore not straightforward DAA candidates.

Body habitus is the other limiting factor. Highly muscular thighs restrict the tissue mobility that DAA depends on for femoral exposure; significant abdominal pannus can obscure the groin incision site and compromise wound healing. Neither group is categorically excluded by clinical rule, but operating conditions become materially more difficult, and most experienced surgeons direct these patients toward approaches offering broader exposure.

Revision arthroplasty and cases involving complex bony deformity or previous hip surgery almost always require that broader exposure — another reason the anterior route remains a primary-surgery technique in the majority of units that offer it.

Body habitus, bone morphology, and soft-tissue status are therefore central questions in any surgical planning conversation, not secondary details — which is why a thorough consultant-led assessment is the starting point for matching the right approach to the individual patient.

Long-term outcomes: where anterior and posterior approaches converge

Clinical trials and systematic reviews tell a consistent story: by six to twelve months after surgery, pain scores, functional outcomes, Harris Hip Score, implant position, and complication rates are broadly equivalent between the anterior and posterior approaches. A multicentre prospective randomised controlled trial that followed patients for 55 months found no statistically significant difference in any of these measures beyond the early post-operative period, and multiple systematic reviews published in 2024 and 2025 have reached the same conclusion. No robust randomised evidence yet demonstrates superiority for either approach in implant survival beyond ten years; claims in both directions rest largely on shorter-term trials or national registry data.

The DAA advantage is genuine, but tightly bounded. Patients recover faster in the first four to six weeks — walking sooner, needing mobility aids for less time, reporting less early pain. For the patient experiencing that first month, the difference is meaningful. But it does not appear to persist. By six months, the two groups are effectively indistinguishable on every standard measure.

Dislocation rates do favour the anterior approach in the majority of comparative studies — the muscle-sparing entry point removes the posterior soft-tissue disruption historically linked to posterior dislocation. This advantage narrows considerably, however, when the posterior approach includes meticulous posterior capsular repair; that technical refinement substantially closes the gap.

For an established surgeon whose posterior technique already carries a reliable track record, a recovery benefit limited to the first few post-operative weeks offers a limited justification for accepting the transition risk of restarting a 100-case learning curve — particularly when long-term implant survival data remain too immature to tip the balance decisively either way.

Muscle-sparing posterior approaches as a middle path

Muscle-sparing posterolateral approaches address a gap that standard posterior technique with capsular repair — however carefully executed — does not fully close. Capsular repair restores structural containment, but it cannot preserve the mechanoreceptors embedded in the short external rotators: the piriformis and obturator internus that SPAIRE (saving piriformis and internus, repair of externus) leaves intact. These structures supply the hip's proprioceptive feedback. Conventional approaches, even with repair, sever them and leave the joint dependent on tissue regeneration for that neurological continuity to return; SPAIRE maintains it from the point of wound closure.

The preserved posterior tension carries a secondary intraoperative benefit: it gives the surgeon real-time tactile feedback on leg length and femoral offset during component placement. DAA surgeons address this differently — typically through fluoroscopy, relied upon by 56.7% of anterior-approach practitioners, or robotic assistance — adding the equipment dependency and theatre complexity discussed in the earlier section on logistical barriers. SPAIRE requires neither a traction table nor that fluoroscopy reliance, and retains the broader anatomical exposure of the posterior route, including access to the hip abductor tendons noted in the patient-selection section as beyond the anterior approach's reach.

These advantages do not make SPAIRE the appropriate choice for every patient. Complex revisions, significant bony deformity, or prior posterior hip surgery may change the surgical calculus. The technique's profile — low dislocation risk, proprioceptive preservation, no specialist table or fluoroscopy dependency — is most relevant to patients seeking primary hip replacement with intact posterior soft tissue, and individual assessment remains the only reliable way to determine suitability.

Prof Paul Lee, whose published work on the SPAIRE technique informs this site's clinical perspective, assesses individual suitability in clinic; Hip Replacement Lincolnshire accepts patients without referral.