What the approach decision actually changes for patients

Long-term implant survival is broadly equivalent whichever of the five principal surgical approaches is used — evidence from large registry studies and head-to-head trials consistently shows no meaningful difference in all-cause revision rates or prosthesis longevity at 25 years. The choice of approach does not, in other words, determine how well the hip replacement holds up over decades.

What the approach decision does change, often substantially, is the weeks either side of surgery. The main points of divergence are dislocation risk profile, speed of early recovery, intraoperative blood loss, and exposure to approach-specific nerve symptoms. A patient's individual anatomy, body composition, prior spinal surgery history, and activity expectations bear directly on which of those tradeoffs matters most.

In practice, the realistic choice is often narrowed before patient preference enters the conversation. Surgeon training and case volume, theatre equipment availability, and the complexity of a patient's hip anatomy can each constrain which approaches are genuinely on the table. The sections that follow set out those tradeoffs — not as a ranking, but as a structured comparison designed to support an informed discussion with a specialist.

Standard posterior approach: the widest access option

The posterior approach is the most widely performed technique in hip arthroplasty globally — a status earned by its reliable anatomical exposure, which accommodates complex primary anatomy, revision cases, and patients with large or heavily muscled frames where anterior access becomes technically demanding.

The approach works from behind the hip, dividing the short external rotator tendons — principally the piriformis and obturator internus — to reach the joint capsule. That division disrupts the soft-tissue sling that normally holds the femoral head in the socket, and dislocation is the predictable consequence. In a retrospective study of 13,335 primary procedures, the posterior approach carried a dislocation rate of 1.1%, compared with 0.7% for DAA and 0.5% for lateral-based techniques. Within that posterior-approach cohort specifically, the downstream burden is considerable: 57% of those who dislocate go on to experience multiple events, and 45.6% require complex revision surgery within two years.

Modern repair modifications — including the STAR technique and various piriformis-preserving variants — have narrowed this gap by reconstructing the posterior capsule and reattaching tendons more robustly. The risk is reduced but not eliminated; repaired tissue must heal before offering reliable mechanical protection, which explains why postoperative movement restrictions have historically accompanied this approach.

Against those caveats, the posterior route offers clear operational advantages: it is faster than DAA, produces lower intraoperative blood loss, and is accessible across a wide range of surgeon experience levels — attributes that carry real weight in high-volume practice and anatomically challenging cases alike.

SPAIRE hip replacement: a muscle-sparing posterior approach

SPAIRE — an acronym for Saving Piriformis And Internus, Repair Externus — is a modified posterior approach that reaches the hip joint through the interval between the inferior gemellus and quadratus femoris muscles, leaving the piriformis and obturator internus tendons completely intact. Only the obturator externus, the lowermost of the short external rotators, is divided. The practical distinction from the standard posterior technique described in the previous section is therefore one of preservation versus division: rather than detaching and reattaching the posterior tendon complex, SPAIRE works around it.

Two mechanisms are proposed for why this may reduce dislocation risk. The first is mechanical: the intact tendons maintain continuous soft-tissue tension across the posterior capsule — a 'strap effect' that physically resists femoral head displacement from the socket. The second is neurological: preserved tendons retain their embedded mechanoreceptors, specifically Golgi tendon organs and muscle spindles, which feed continuous positional information to the nervous system. When tendons are divided and repaired, this proprioceptive signalling is interrupted and can take months to recover through neural regeneration; in SPAIRE, it operates from day one. Proponents argue this dual mechanism — mechanical and neurological — gives the hip a biological safeguard that capsular repair and tendon-reattachment strategies cannot replicate immediately after surgery.

The technique was first formalised in 2016 and has since been used in over 1,026 routine primary hip replacements at a single centre since February 2016, routinely combined with Mako robotic assistance from 2018 onwards. Professor Paul Lee, who developed the approach at the Exeter Hip Unit, uses robotic assistance to offset the more limited visual field that the tissue-preserving dissection creates; sub-millimetre bone resection and implant positioning help compensate for what the surgeon cannot expose as readily as in broader-access techniques.

SPAIRE is not suitable for every patient. The technique is more demanding — and the anatomy less forgiving — in patients with small pelvic dimensions, reduced femoral offset, or a fixed external rotation deformity. These are not rare presentations, and appropriate patient selection is central to the approach's safety profile.

On the evidence front, the picture remains incomplete. The NIHR-funded HIPSTER trial — a double-blinded three-arm RCT comparing robotic-assisted piriformis-sparing, SPAIRE, and standard posterior THA — was still recruiting as of 2024, and long-term comparative data against DAA and SuperPATH in large randomised cohorts do not yet exist. The current case for SPAIRE rests on mechanistic reasoning, single-centre series, and intermediate-term outcomes rather than the kind of head-to-head RCT evidence that would settle the comparison definitively.

Direct anterior approach (DAA): early recovery with specific tradeoffs

Among the five approaches, DAA carries the most convincing registry-level dislocation data. A Dutch national study of 269,280 primary hip replacements found the anterior approach had a dislocation revision rate of 0.4% — the lowest of any technique, compared with 1.4% for the posterolateral route, giving an adjusted hazard ratio of 0.3. For patients who have previously undergone lumbar spinal fusion, the benefit is particularly pronounced: in a series of 16,223 cases, prior spinal fusion increased dislocation risk 4.3-fold overall, yet this association was statistically significant only in the posterior approach group (P<0.001) and not the anterior (P=0.514), supporting DAA as the preferred choice in that specific population.

The mechanical explanation is straightforward: DAA works through the internervous plane between tensor fasciae latae and sartorius, reaching the hip capsule without detaching any muscle. This preserves the anterior soft-tissue envelope and eliminates the posterior capsular defect that is the main dislocation vector in standard posterior surgery. One finding worth noting, however, complicates the familiar 'anterior equals stable' narrative: in a retrospective study of 13,335 primary arthroplasties, 58.8% of DAA dislocations occurred posteriorly — suggesting that anterior access does not fully eliminate posterior instability, particularly when implant positioning is suboptimal.

The approach's tradeoffs are well-documented. Intraoperative blood loss is higher than both SPAIRE and SuperPATH. Operative time is longer than the posterior route. A traction table is required, adding equipment dependency and room-set-up constraints. The learning curve carries real clinical consequence: surgeons in earlier stages of DAA experience face a measurably higher risk of intraoperative femoral fracture during canal preparation.

The nerve complication specific to this approach — lateral femoral cutaneous nerve (LFCN) neurapraxia, causing numbness or altered sensation over the outer thigh — was recorded in 4.1% of cases in a dedicated single-surgeon series conducted after the learning curve had been completed. All 17 affected patients had fully recovered at two-year follow-up. Risk factors include vigorous traction, hyperextension, and extreme external rotation during the procedure.

SuperPATH and lateral/Hardinge: where each approach still fits

SuperPATH (Supercapsular Percutaneously Assisted Total Hip) accesses the joint from the posterior side without dislocating the femoral head, instead working through a supercapsular window that preserves the surrounding soft tissue. The perioperative data are strong: a network meta-analysis of 20 RCTs involving 1,501 patients found SuperPATH reduced intraoperative blood loss by a mean of 81.75 mL and produced higher Harris Hip Scores at 3, 6, and 12 months compared with the standard posterior approach. Against DAA, SuperPATH showed shorter operative incision, lower blood loss, and shorter hospitalisation, though the two approaches performed comparably on functional outcomes and acetabular cup positioning across a 16-RCT analysis of 1,392 patients.

Where the evidence thins is beyond the short term. Long-term revision and functional data are genuinely limited — SuperPATH's registry footprint does not yet match the depth available for posterior or DAA series, and this gap matters when weighing approaches for younger, higher-demand patients. Patient selection is also a hard boundary: the technique is validated in mild acetabular dysplasia (Crowe Types I–II), where JOA scores improved from 48.8 to 91.5 at two months in one series, but it has not been evaluated for severe dysplasia (Crowe III–IV), major bone loss, or complex revision. Operative time is consistently longer than posterior, and the learning curve is steep.

The lateral (Hardinge) approach occupies a different position. NICE recommends it as the standard for hip hemiarthroplasty, and it remains a comparator in major UK trials, including an NIHR-funded multicentre RCT comparing HemiSPAIRE against the standard lateral approach for displaced intracapsular femoral neck fractures (recruited November 2019–April 2022). In elective primary total hip arthroplasty, its use is declining at high-volume centres. Dutch registry data from 269,280 procedures show a dislocation revision rate of 0.6% — lower than the posterolateral route — but the highest overall revision rate of any approach studied, a tradeoff that shapes its diminishing role in routine elective surgery.

Patient suitability: how surgeons match approach to individual

Matching approach to patient begins not with the surgeon's preferred technique but with a short list of clinical variables that genuinely shift the risk calculus.

Prior lumbar spinal fusion is the clearest single flag. Registry data from 16,223 cases show a 4.3-fold increase in dislocation risk via the posterior route for these patients; the anterior approach (OR 0.64) and lateral-based approaches (OR 0.42) were significantly protective by comparison, making DAA the logical choice where anatomy permits it.

Body habitus and working anatomy cut differently across techniques. DAA creates measurable challenges in biomechanical reconstruction in larger or more muscular patients, while SPAIRE's tissue-preserving corridor can be restricted by small anatomy, reduced femoral offset, or fixed external rotation deformity. Complex primary anatomy, revision cases, and heavily muscled frames typically require a standard posterior approach for adequate exposure — no minimally invasive technique resolves every anatomical situation.

Surgeon and unit experience matters as much as technique selection. DAA and SuperPATH both carry steep learning curves with documented intraoperative complication profiles; a technically well-matched approach delivered by a high-volume surgeon will consistently outperform a theoretically superior technique used by a surgeon earlier in their adoption curve.

For patients at the decision stage, three questions are worth raising at any surgical consultation: whether prior spinal surgery or known spinal stenosis changes the recommended approach; what the surgeon's annual case volume is for the specific technique proposed; and whether the centre contributes to a national implant registry whose outcomes data are publicly available. The answers to those three questions carry more practical weight than any headline comparison between approaches.

1. [1] How does Surgical Approach affect Characteristics of Dislocation after Primary Total Hip Arthroplasty?. (2023). https://doi.org/10.1016/j.arth.2023.05.034 https://doi.org/10.1016/j.arth.2023.05.034
2. [2] Femoral head size and surgical approach affect dislocation and overall revision rates in THA: Dutch Arthroplasty Register (269,280 procedures). (2023). https://doi.org/10.1177/11207000231160223 https://doi.org/10.1177/11207000231160223
3. [3] Comparison of SuperPath vs modified Hardinge approach in THA for femoral neck fractures: a randomized controlled trial. (2023). https://doi.org/10.1186/s13018-023-03713-9 https://doi.org/10.1186/s13018-023-03713-9
4. [4] Does Surgical Approach Affect Dislocation Rate After THA in Patients with Prior Lumbar Spinal Fusion? (16,223 cases). (2024). https://doi.org/10.1016/j.arth.2024.03.068 https://doi.org/10.1016/j.arth.2024.03.068
5. [5] 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
6. [6] Direct and indirect comparisons in network meta-analysis of SuperPATH, direct anterior and posterior approaches in total hip arthroplasty. (2022). https://doi.org/10.1038/s41598-022-20242-3 https://doi.org/10.1038/s41598-022-20242-3
7. [7] Minimally invasive SuperPath arthroplasty: Applicability to mildly dysplastic osteoarthritis and early recovery of lower limb function. (2023). https://doi.org/10.23750/abm.v94i3.13922 https://doi.org/10.23750/abm.v94i3.13922
8. [8] Meralgia Paresthetica — Approach-Specific Neurological Complication in DAA Total Hip Replacement. (2024). https://doi.org/10.3390/life14010151 https://doi.org/10.3390/life14010151