Hemi or total hip replacement — the first decision after a neck of femur fracture

A displaced femoral neck fracture leaves little room for delay. In the vast majority of cases, surgery within 36–48 hours is the standard of care — conservative management carries unacceptably high risks of complications, prolonged bed rest, and mortality in older adults. The immediate clinical question is not whether to operate, but what operation to perform.

The first fork in the decision tree is hemiarthroplasty versus total hip replacement (THA). Hemiarthroplasty replaces only the femoral head with a prosthetic implant, leaving the natural acetabular socket untouched. THA replaces both the femoral head and the socket, reconstructing the entire joint. For most patients presenting with a femoral neck fracture, the choice between these two operations turns on fitness and frailty rather than the fracture pattern itself — a fitter, more cognitively intact patient may gain more from a THA, while a frailer patient is more likely to be best served by the shorter, less demanding hemiarthroplasty procedure.

The Nottingham Hip Fracture Score (NHFS) provides a practical framework for quantifying that risk. In a study of 1,210 displaced intracapsular fracture patients, those who received hemiarthroplasty were on average older (82.2 versus 74.6 years), carried a higher mean NHFS (6.0 versus 3.5), and faced substantially higher 1-year mortality (36.2% versus 3.5%) compared with those who received THA. Importantly, within the NHFS 4–6 subgroup — patients with intermediate frailty — THA was associated with a 1-year mortality of just 3.4% compared with 29.6% for hemiarthroplasty, alongside higher rates of discharge directly to home. The NHFS is not a standalone decision rule, but it illustrates why matching implant extent to patient physiology matters enormously.

Once hemiarthroplasty is selected as the appropriate procedure, a second and equally consequential question arises: through which surgical approach should it be performed? That is where SPAIRE becomes relevant. The SPAIRE technique does not alter who receives hemiarthroplasty rather than THA; it determines how that hemiarthroplasty is carried out — and the choice of approach has measurable consequences for dislocation risk, early mobility, and functional recovery.

What the SPAIRE approach actually does to the hip joint

Running across the back of the hip joint — the ball-and-socket formed by the femoral head sitting inside the acetabulum — are several small rotator tendons that do more than move the leg. They act as a passive restraint, holding the femoral head in place against posterior displacement. SPAIRE (Save Piriformis And Internus, Repair Externus) is a modified posterolateral approach whose name spells out exactly what is preserved and what is not.

In a standard posterior approach, the piriformis tendon and the conjoint tendon of the obturator internus and gemelli muscles are both divided to gain access to the joint. SPAIRE leaves these two structures completely undisturbed. The only soft-tissue sacrifice is the obturator externus tendon, which is sectioned to allow adequate exposure and then repaired at the end of the procedure. This single-tendon division is what distinguishes SPAIRE from its conventional posterior predecessor, originally described as the Modified Posterior Approach by Kim et al. in 2008.

The mechanical consequence of keeping the piriformis and obturator internus intact is straightforward: those tendons form a continuous strap across the back of the joint that resists backwards translation of the femoral head. Beyond mechanics, there is a neurological dimension. The preserved tendons contain Golgi tendon organs and muscle spindles — mechanoreceptors that relay continuous proprioceptive signals to the central nervous system. When these structures are severed, that feedback is interrupted; the hip loses its reflexive protection against extreme positions until nerve regeneration occurs. Intact tendons maintain this signalling from the moment the patient wakes from anaesthesia.

The direct lateral approach, which accesses the hip from the side rather than the back, avoids the posterior tendons altogether but requires splitting the gluteus medius — a much larger weight-bearing muscle — to reach the joint. This trade-off has its own implications for early walking ability, which the next section addresses directly.

The dislocation-mobility dilemma SPAIRE was designed to resolve

No single conventional approach to hip hemiarthroplasty solves all the problems at once — that is the honest starting point for understanding why SPAIRE exists.

The standard posterolateral approach offers good surgical access and wide familiarity, but carries a meaningful dislocation penalty. A JAMA Network Open study of 843 patients confirmed it was associated with significantly more dislocations and reoperations than the direct lateral approach. The direct lateral route addresses this risk, but at a cost: splitting the gluteus medius can produce abductor weakness and a limp that persists well into the recovery period, slowing the patient's return to independent walking.

The direct anterior approach (DAA) appeared to offer a third path, bypassing both the posterior tendons and the abductor muscle. Proponents argued it would deliver faster functional recovery. In practice, the evidence has not supported this claim. A 2025 Charnley Award RCT of 102 patients found Barthel-20 scores were identical in the anterior and lateral groups at six weeks (15.8 in both, p=0.98), with no differences in pain, length of stay, or 90-day mortality — and its authors did not recommend widespread adoption given the learning curve and specialist equipment requirements. A nine-centre cohort study of 956 hemiarthroplasty patients added a more serious concern: the direct anterior approach was independently associated with 7.3 times the risk of periprosthetic joint infection at 90 days.

SPAIRE does not resolve this dilemma definitively, but it targets both problems from the posterolateral side. Retaining the posterior soft-tissue restraints aims to provide the stability the standard posterolateral approach lacks, without the abductor disruption associated with the lateral route. A secondary practical benefit is that intact capsular and tendinous attachments serve as a reliable intraoperative anatomical reference, helping the surgeon assess leg length and femoral offset accurately during the hemiarthroplasty itself.

What the clinical evidence shows for SPAIRE in hemiarthroplasty

The strongest direct evidence for SPAIRE in hemiarthroplasty comes from a 2025 Norwegian registry study of 858 cases — 430 treated with SPAIRE, 428 with the direct lateral approach. Dislocation rates were statistically indistinguishable (0.7% versus 0.9%), but at three months SPAIRE patients recorded significantly better New Mobility Score (6.1 versus 5.0), Short Physical Performance Battery score (7.3 versus 5.9), and walking speed (0.8 versus 0.7 m/s), with no difference in surgical site infection or 30-day mortality.

A UK single-centre retrospective series of 194 hemiarthroplasty cases reinforces this picture. Zero dislocations occurred in the SPAIRE group, against 2% in the anterolateral group and 3.7% in the standard posterior group — figures that carry particular weight in a patient population already at elevated risk of falls. Mean time to mobilisation was 1.4 days with SPAIRE, compared with 2.0 days for the anterolateral group and 2.6 days for the standard posterior group, with comparable surgical times across all three.

The pattern that emerges from a pair-matched control study of 240 cemented hemiarthroplasty patients is instructive about what SPAIRE does and does not deliver. At 30 days, only 8.1% of SPAIRE patients had dropped a mobility level from their pre-fracture baseline, versus 31.6% in the direct lateral group (p=0.003). By 120 days, that difference was no longer statistically significant. A PRISMA systematic review of 1,385 hips across multiple study designs confirms exactly this trajectory: early advantages in mobility and pain management, with no consistent between-group separation in long-term patient-reported outcomes, discharge destination, or bone health markers.

One limitation deserves stating plainly: no published randomised controlled trial has used SPAIRE against the direct lateral approach as its primary comparison, and patient-reported outcome data beyond three months remain sparse. These are not reasons to dismiss the existing evidence — the registry data and matched cohorts are substantial — but they mark where clinical certainty ends and where further research is needed.

Patient suitability — who benefits most and when SPAIRE may not apply

Certain patients are more likely to gain measurable benefit from SPAIRE than others — and being clear about this matters as much as knowing what the technique does.

SPAIRE is a posterolateral approach, and that architecture determines both its strengths and its limits. Patients who stand to benefit most are those where preserving early mobility is clinically urgent: older adults at significant risk of rapid deconditioning, those whose functional reserve is already narrow, and patients for whom swift return to weight-bearing reduces secondary complications such as pressure injury or chest infection. The evidence — particularly the 30-day data showing only 8.1% of SPAIRE patients dropping a mobility level versus 31.6% in a matched direct lateral group — reflects a genuine early-recovery advantage in this profile.

SPAIRE is not suitable for every presentation. Patients with pre-existing severe posterior soft-tissue damage, prior hip surgery creating capsular scarring, or unusually complex anatomy may not be candidates for this modified posterolateral dissection. Revision scenarios, in which the relevant anatomy is already disturbed, present similar constraints. The technique also requires precise dissection to preserve the piriformis and obturator internus without compromising the surgical field — it is not a routine variation on a standard posterior approach, and surgeon case volume is a genuine consideration rather than a formality.

This section assumes hemiarthroplasty is already confirmed as the appropriate operation; where total hip replacement may be more suitable, that decision should be made first (see above).

Before any approach is selected, a pre-operative assessment should cover fracture pattern, functional status, and baseline mobility. A practical question to raise at that stage: whether the operating surgeon has performed SPAIRE specifically, not merely the standard posterolateral approach.

Getting a specialist assessment for hip replacement after a femoral neck fracture

Choosing between hemiarthroplasty and total hip replacement — and between surgical approaches — is most usefully made with a surgeon who has direct, case-volume experience of the specific technique under discussion. Several practical questions are worth raising at any pre-operative consultation: how many SPAIRE procedures the surgeon has performed (as distinct from the standard posterolateral approach); how the hemi-versus-THR decision is reached for patients whose frailty scores sit in the borderline range; and what functional outcomes the centre routinely measures at 30 days and three months. These are reasonable, evidence-grounded questions, and a surgeon experienced in the area should answer them without hesitation.

Professor Paul Lee trained at the Exeter Hip Unit under Professor Timperley and has published clinical work on the SPAIRE technique specifically in hemiarthroplasty for displaced intracapsular neck of femur fractures — a relatively uncommon combination of approach expertise and fracture-specific case experience. Patients seeking a consultant-led assessment of their hip replacement options, including which approach may be appropriate, can be seen at Sleaford (NG34) or Grantham (NG31) through Hip Replacement Lincolnshire, part of the MSK Doctors group, without GP referral or NHS-style waiting. Appointments can be arranged directly at hipreplacementlincolnshire.co.uk.

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