Why the surgical route into the hip matters

When a hip joint is replaced, the implant itself is the same whichever route the surgeon takes. What changes — and what matters considerably to recovery — is the path used to reach it.

Every approach requires the surgeon to move through layers of muscle, tendon, and capsule before the damaged joint is exposed. How much of that tissue is cut, stretched, or left untouched determines how the body heals afterwards. A more disruptive route may give excellent surgical visibility; a less disruptive one may spare structures that protect the new joint from dislocation and allow movement to return sooner. Neither trade-off is trivial.

The practical consequences for patients include how long movement restrictions apply, whether the hospital stay runs to days or hours, and how stable the hip feels in the weeks before surrounding soft tissues have fully settled. Surgeons weigh these factors against anatomy, their own training, available technology, and what matters most to the individual in front of them. Understanding those trade-offs is a reasonable starting point for any patient heading into this conversation.

The posterior approach: the most common route and its limitations

Reaching the hip from the back — the posterior approach — has been the dominant method in the UK and across most of the world for decades, and for good reason. The patient lies on their side while the surgeon makes a curved incision of around four to six inches near the buttock, splits the gluteus maximus along its fibres, and then cuts two short external rotator tendons — the piriformis and obturator internus — to expose the joint capsule beneath. This gives outstanding visibility of the acetabulum and femoral head, and the exposure accommodates a wide range of patient anatomies, body types, and more complex revision cases with few technical constraints.

At the end of the procedure, those tendons are repaired and sutured back to bone. That repair is consequential. Until the reattached tissue heals and regains meaningful strength, the reconstructed posterior capsule is the primary defence against the new implant dislocating. Surgeons therefore ask patients to observe strict movement precautions for approximately six to eight weeks: no bending the hip beyond 90°, no crossing the legs, no rotating the leg inward. These rules exist because the soft tissues need time — not because the implant itself is insecure. Hospital stays of three to five days are typical, partly to ensure patients can manage those restrictions safely at home.

The historical dislocation risk associated with the posterior route has fallen as capsular repair techniques have improved, and many patients recover well within its framework. It remains a well-executed and widely taught procedure; most orthopaedic surgeons are highly trained in it. Its recovery timeline, though, reflects the tissue disruption at its core — and it is that disruption which has driven interest in approaches designed to avoid making those cuts in the first place.

The direct anterior approach: early recovery gains and surgical trade-offs

Approaching the hip from the front — the direct anterior approach — follows a different logic entirely. Rather than cutting through tendons to gain access, the surgeon works through the natural interval between two muscles at the front of the groin: the tensor fasciae latae and the sartorius. These muscles are separated, not divided, so most of the surrounding tissue is left intact.

That distinction has real consequences in the early post-operative period. Patients typically experience less pain in the first days after surgery, can move with fewer restrictions almost immediately, and — in selected cases — may be discharged on the day of the operation or the following morning. The approach has grown considerably in popularity over the past ten to fifteen years, particularly in the United States, where it is now used routinely at many high-volume centres.

The trade-offs, however, are clinically significant and worth understanding plainly. The direct anterior approach is technically more demanding than the posterior route: the operating position is less forgiving, the surgical window is narrower, and there is a higher risk of fracture of the femur during implant insertion, as well as a greater chance of irritating the lateral femoral cutaneous nerve — a sensory nerve running close to the incision that can cause numbness or burning along the outer thigh. These are not rare complications, and the learning curve for surgeons is steeper.

The approach also has a specific anatomical blind spot: if the gluteus medius or minimus tendons are damaged or torn — a finding more common in older patients — they cannot be assessed or repaired through this exposure.

By three to six months, published data suggest that outcomes for anterior and posterior hip replacement are equivalent in terms of function and pain relief; the implant used is identical across both approaches. The genuine advantage of the direct anterior route sits in that earlier window — and for some patients, that window matters considerably.

Muscle-sparing surgery: what the SPAIRE technique preserves and why it matters

SPAIRE — Saves Piriformis And (Obturator) Internus with Repair of (Obturator) Externus — begins with a different premise: the tendons do not need to be cut at all. First described by Kim et al. in 2008 as a modified posterior approach, it uses the same posterior route but navigates carefully around the piriformis and obturator internus, leaving both entirely intact. Only the obturator externus is repaired at closure.

That preservation has three interlocking biological consequences.

The first is structural. The intact obturator internus passes directly over the posterior femoral head, creating what surgeons call a 'strap effect' — a dynamic tether that actively resists dislocation from the moment the patient wakes from surgery. Because this stabiliser is present immediately rather than weeks later after tendon re-healing, post-operative movement restrictions can generally be lifted entirely.

The second consequence is neurological. Preserved tendons retain their Golgi tendon organs and muscle spindles — mechanoreceptors that relay joint position to the nervous system in real time. A patient walking the day after surgery has an intact system communicating where their hip is in space, rather than a neurologically quietened joint still waiting for those signals to return. That continuous proprioceptive feedback from day one may help explain the technique's very low dislocation rates.

Third, intact soft tissues provide reliable intraoperative reference points for judging leg length and femoral offset during implant placement, reducing the risk of post-operative limb-length discrepancy. Mako robotic assistance can be integrated to extend that accuracy to sub-millimetre precision.

It is worth stating plainly that head-to-head randomised trial data comparing SPAIRE directly against the direct anterior approach in large patient cohorts is not yet available; most comparative evidence rests on biomechanical reasoning and published case series. What those sources consistently support is that the biological rationale is sound. For selected patients — particularly those for whom early stability and an unrestricted recovery are priorities — same-day or next-day discharge becomes a realistic outcome within this pathway.

How surgeons match the approach to the patient

Choosing a surgical approach is rarely a simple preference. Anatomy, body composition, prior operations around the hip, the condition of the surrounding tendons, and the specific implant selected all shape which route gives the surgeon adequate working conditions and the patient the safest outcome.

The direct anterior approach, for instance, is not universally applicable. In patients with a higher BMI, certain femoral shapes, or significant soft-tissue depth, the anterior window can be too restricted to place components accurately — and proceeding regardless raises the risk of malalignment or femoral fracture. The posterolateral route, including SPAIRE, accommodates a broader range of anatomy, partly because the surgical field is less constrained by the patient's build.

Within the anterior category, too, meaningful technical variation exists. A 2023 systematic review and meta-analysis of 3,716 patients found that the anterior-based muscle-sparing (ABMS) approach produces equivalent outcomes to the direct anterior route across all measured variables — perioperative results, complications, and implant position — while offering the surgical team fewer positional constraints. Equivalent outcomes reached by different technical routes underscores that no single method dominates.

The decision itself belongs in pre-operative assessment, not in the operating theatre. Imaging, functional history, limb-length considerations, and a frank discussion of recovery expectations all inform the plan before the patient arrives for surgery. A surgeon who works comfortably across multiple approaches — selecting between a muscle-sparing posterior technique, an anterior access route, and hip resurfacing according to what each assessment reveals — is better placed to arrive at a genuinely matched choice than one for whom only one option is available. That is the principle underlying how Professor Paul Lee approaches individual patient planning, selecting on clinical grounds rather than defaulting to a fixed method regardless of anatomy.

Recovery expectations across the three approaches

Recovery speed captures most of the public discussion about surgical approaches, but it is only one dimension of what patients actually experience in the weeks and months after hip replacement.

Long-term outcomes tell a more level story. By one year, functional scores, pain relief, and implant survivorship are broadly comparable across well-performed posterior, anterior, and muscle-sparing procedures — the choice of route does not, on current evidence, significantly alter the durability of a hip replacement over time. The same implant is placed regardless of which approach is used.

Where the approaches genuinely diverge — beyond the early mobilisation differences covered earlier — is in their distinct complication profiles. The direct anterior route carries a documented higher risk of lateral femoral cutaneous nerve irritation, a numbness or tingling along the outer thigh that resolves in most patients but can persist. The posterior approach, when tendon repair is performed, introduces a dislocation risk during the healing window even with precautions followed carefully. Muscle-sparing posterolateral techniques shift that risk profile by preserving the biological stabilisers outright, though their comparative evidence rests on case series and biomechanical reasoning rather than large randomised trials.

These distinctions are precisely what a pre-operative conversation should surface. Useful questions include: which tendons, if any, will be divided and over what timeframe their healing is expected; what movement restrictions will be imposed and for how long; and whether a same-day discharge pathway exists at the centre where surgery is planned. The right approach is chosen with the right surgeon — and understanding the trade-offs before consenting is what makes that choice genuinely informed.