What each approach actually does to your hip

When two surgeons recommend different approaches to hip replacement, the question most patients ask first is: does the route in change what gets put in? It does not. Whether a surgeon uses SPAIRE or the Direct Anterior Approach (DAA), the prosthetic components — the acetabular cup, the femoral stem, and the bearing surface — are identical. The tradeoffs lie entirely in how the surgical team reaches the joint.

SPAIRE (Saving Piriformis And Internus, Repair Externus) is a muscle-sparing modified posterior approach. The surgeon works from behind the hip and divides only one tendon — the obturator externus — leaving the piriformis, the obturator internus, and the rest of the short external rotator group completely intact throughout the procedure. Think of these tendons as a set of stabilising straps at the back of the hip: SPAIRE keeps them in place and under tension.

DAA enters the hip from the front, exploiting a natural gap — an internervous plane — between the tensor fasciae latae and the sartorius and rectus femoris muscles. No muscle is deliberately cut, which is why it is described as an internervous approach. The trade-off is that this anterior corridor is narrower and typically demands precise patient positioning, often using a specialised traction table and intraoperative X-ray guidance to achieve accurate implant placement.

In short: same hip replacement, different anatomical route. What changes between the two approaches is the set of tissues encountered along the way — and it is those differences that shape everything from early recovery to approach-specific complication risk.

Where the two approaches produce the same result

For all the genuine differences in surgical route, the headline finding from comparative studies is straightforward: neither approach outperforms the other in implant survival or all-cause revision rates. A 2016 randomised study by Malek et al. comparing DAA and posterior approaches under Enhanced Recovery protocols found no statistically significant difference in clinical outcomes — and retrospective series examining longer follow-up periods have consistently echoed that finding. At a population level, roughly 58% of total hip replacements are estimated to survive 25 years, a figure driven by implant choice, bearing surface, bone quality, and patient activity — not by which side of the hip the surgeon entered.

Post-operative movement restrictions are another area of convergence. The traditional 'hip precautions' — strict limits on bending and crossing the legs — were a feature of older posterior technique. Modern approaches on both sides have largely moved away from them: SPAIRE's intact tendon strap provides immediate mechanical stability from behind, while DAA's anterior position confers inherent stability from the front.

Both approaches are also fully compatible with Mako robotic-arm assistance, which improves component positioning accuracy independently of which access route is used. This means that where a surgical team uses robotic guidance, the precision benefit is available whichever technique is chosen.

The practical implication for patients is freeing rather than limiting: if your surgeon is skilled in either technique, the replacement itself will last just as long either way. The meaningful comparison lies not in longevity but in the specific tradeoffs each route introduces — and those are worth examining carefully.

DAA's genuine advantages in early recovery

The absence of deliberate muscle division is what gives DAA its most consistent clinical advantage. Because the approach displaces rather than cuts the surrounding muscles, there is typically less mechanical trauma to soft tissue in the immediate post-operative period — and displaced tissue recovers faster than divided tissue. Patients often report lower early muscle soreness compared with any posterior approach, including SPAIRE.

Across comparative series, this translates to a slightly faster return to functional baseline in the first one to three months: earlier independent walking, faster discharge, and modestly better Harris Hip Scores at six and twelve weeks. For patients with pressing occupational demands or personal commitments within that window, the early edge is clinically meaningful, not merely statistical.

The advantage is, however, time-limited. Beyond roughly three months, functional outcomes between the two approaches converge substantially, and studies find no consistent difference by the one-year mark.

The early-recovery benefit comes alongside a specific risk profile that patients should understand. DAA involves longer operative times and modestly higher intraoperative blood loss than posterior approaches. Lateral femoral cutaneous nerve (LFCN) neurapraxia — causing numbness or tingling at the outer thigh — is the approach's most characteristic complication. The technique also carries a steeper learning curve, with higher rates of periprosthetic femoral fracture during canal preparation in less experienced hands.

Where SPAIRE offers distinct clinical advantages

Three distinct advantages set SPAIRE apart — two mechanical, one practical — and they are worth distinguishing clearly from theoretical claims.

The most directly evidenced is posterior stability. In a standard posterior approach, the short external rotator tendons are divided and reattached; their protective effect depends on how well that repair heals. In SPAIRE, the obturator internus tendon is never cut. It runs directly over the posterior femoral head at the centre of rotation and, kept under its natural tension, acts as an immediate structural tether. There is no healing phase, no reattachment to wait on. Published case series from practices using SPAIRE across more than 1,000 consecutive primary total hip replacements report very low posterior dislocation rates — meaningfully lower than those historically associated with standard posterior technique. That outcome is consistent with the mechanism.

The second advantage — preserved proprioception — is mechanistically compelling and supported by that same dislocation signal. Golgi tendon organs and muscle spindles embedded within the intact short external rotators continue to send afferent position signals to the central nervous system immediately after surgery. Approaches that sever these tendons interrupt that feedback until biological healing restores it. Whether preserved proprioception produces measurable functional gains beyond stability in a blinded RCT is what the ongoing NIHR-funded HIPSTER trial is designed to establish; those results are not yet available.

Practically, SPAIRE also suits a broader range of body types. DAA's narrow anterior corridor becomes more demanding — and carries higher complication risk — in larger or more muscular patients. SPAIRE does not rely on that corridor. It also requires no specialised traction table or intraoperative fluoroscopy, making its results less dependent on equipment availability across different surgical settings.

Which patients tend to suit each approach

Patient anatomy — not surgeon preference — should drive this decision, and the honest starting point is build and body type.

For lean or moderately built patients with straightforward hip anatomy, DAA's narrow anterior corridor is reliably accessible. The approach works within a tighter window, and when that window is comfortably available, its early-recovery profile is a genuine clinical asset. Patients who had prior groin or inguinal surgery face a specific additional consideration: existing scarring in that territory may complicate anterior access and heighten the risk of nerve involvement in that region.

For larger-framed or more muscular patients, SPAIRE's posterior route becomes the stronger technical option. The anatomical demands that narrow DAA's margin of safety simply do not apply in the same way from a posterior entry. SPAIRE also allows the surgeon to directly assess and address the abductor tendons — gluteus medius and minimus — if pathology is found intraoperatively. DAA cannot access or repair those structures at all.

Surgeon volume matters as much as anatomy. A surgeon operating with consistently high SPAIRE case numbers will, in practice, produce lower complication rates than a surgeon with limited DAA experience — and the reverse holds equally. Approach comparisons in isolation cannot account for this.

The most useful heuristic for a consultation: if your build is larger than average and your surgeon's SPAIRE volume is substantial, the evidence tilts clearly. If you are lean, anatomically straightforward, and your surgeon's DAA series is extensive, the faster first month becomes a legitimate priority. Specialist anatomical assessment is what converts those general tilts into an individualised recommendation.

Getting the right surgical assessment

The approach decision ultimately comes down to factors no comparison article can resolve: a patient's anatomy, the surgical team's experience, and what matters most in the weeks immediately after surgery.

A structured pre-operative assessment works through each of these methodically — build and body type, pelvic anatomy, activity goals, any coexisting abductor pathology, and the volume of cases a surgeon brings to their preferred technique. Professor Paul Lee, who has used the SPAIRE technique across more than 1,000 primary total hip replacements and is actively engaged with the evidence emerging from the NIHR-funded HIPSTER trial, applies that case-series depth to every surgical consultation. Until HIPSTER results are published, approach selection in this area rests on exactly that combination: prospective trial awareness, granular operative experience, and patient-specific anatomical assessment — not a fixed preference for one route.

An objective pre-operative gait assessment, using tools such as MAI Motion®, can document a functional baseline and clarify post-operative rehabilitation targets whichever approach is chosen — a useful adjunct when setting realistic recovery goals before surgery.

Patients considering either SPAIRE or DAA can arrange a consultant-led assessment at Hip Replacement Lincolnshire (part of MSK Doctors) without a GP referral and without NHS-style waiting lists, at clinics in Sleaford (NG34) and Grantham (NG31) — visit hipreplacementlincolnshire.co.uk.

1. [1] An anatomic consideration of the femoral nerve during direct anterior hip approach: A cadaveric study. (2024). https://doi.org/10.1007/s00276-024-03364-3 https://doi.org/10.1007/s00276-024-03364-3
2. [2] A Standard of Care in Hip Arthroplasty: Routine Use of the Tendon-Sparing SPAIRE Technique with MAKO Robotic Assistance. (2024). https://doi.org/10.1302/1358-992x.2024.16.030 https://doi.org/10.1302/1358-992x.2024.16.030
3. [3] THE SPAIRE TECHNIQUE ALLOWS HIP ARTHROPLASTY WITH DIVISION OF ONLY THE OBTURATOR EXTERNUS TENDON. (2018).