The four risks patients most often ask about

Asking about risk before a hip replacement is not pessimism — it is good judgement. Four complications account for most of the questions surgeons hear: dislocation, infection, periprosthetic fracture, and nerve injury. Each is real, each carries a measurable probability, and none is simply a matter of luck.

The numbers vary considerably by category. Dislocation is the most discussed, with primary rates spanning roughly 0.2% to 10% depending on patient profile and surgical approach; in already-revised hips the figure can reach 28%. Deep periprosthetic joint infection affects around 1–2% of first-time replacements. Periprosthetic fracture — a break in the bone around the implant — occurs in approximately 0.4–3.5% of cases. Nerve injury is the least common, arising in under 1% of primary procedures.

These figures are starting points, not sentences. Every one of the four risks is shaped by patient-specific factors, the surgical approach chosen, and how carefully the operation is planned. Understanding what drives each risk — and where surgical judgement can shift the odds — is the practical value of looking at them in detail. The sections that follow do exactly that.

Dislocation: the risk with the heaviest downstream burden

Dislocation attracts more clinical attention than its raw probability might suggest, and the reason lies in what tends to follow. The joint simply loses contact — the femoral head slips out of the acetabular cup — and whilst a single episode can usually be reduced under anaesthesia, that first event substantially increases the likelihood of further ones.

Timing matters here. The first 90 days after surgery represent the highest-risk window across all approaches, coinciding with the period during which divided capsular and tendinous tissues are still healing. Once that biological repair is complete, baseline stability improves — but for patients who dislocate before it does, the picture can become considerably more complicated.

The downstream numbers are worth understanding clearly. More than 57% of patients who experience a dislocation will go on to have at least one further episode; roughly one in ten will dislocate more than five times. Approximately 45.6% require complex revision surgery within two years. Revision hip replacement carries its own elevated risk profile and is substantially more demanding than primary surgery — which is precisely why preventing the first dislocation matters so much.

Certain patient characteristics are associated with higher individual risk: age under 65, female sex, a BMI below 20, neuromuscular conditions such as Parkinson's disease or prior stroke, and a higher burden of comorbidities. None of these factors can be fully modified, but they are not grounds for fatalism either. They are the reason pre-operative risk assessment exists — so that the surgical approach, implant selection, and planning can be calibrated to the individual rather than applied as a default.

Infection, fracture, and nerve injury: what patients need to know

One aspect of infection that surprises many patients is that the risk does not end when the wound closes. Deep periprosthetic joint infection — the more serious scenario, affecting around 1–2% of first-time replacements — can arise months or years after apparently uncomplicated surgery, seeded by bacteria travelling through the bloodstream from a remote source: a dental procedure, a urinary tract infection, a chest infection, or a skin break. Superficial wound infections may respond to antibiotics, but deep infection involving the prosthesis typically requires surgical washout or, in the most serious cases, removal and staged replacement of the implant. This is why many surgeons advise antibiotic cover for certain dental work in the years following hip replacement — a practical implication worth understanding well before surgery.

Periprosthetic fracture — a break in the bone around the implant — is the third most common reason for revision hip surgery. Risk is not evenly distributed: older women with osteoporosis and patients undergoing revision procedures (where bone is already weakened by prior implant removal) carry a higher burden. Cementless press-fit stems also require precise canal preparation, and intraoperative fracture risk rises during a surgeon's learning curve with any new technique. Management depends on fracture stability and may involve plates, screws, or cerclage wires, sometimes combined with a longer revision stem.

Nerve injury is the rarest of the four but leaves a disproportionate mark when it occurs. The peroneal branch of the sciatic nerve is most commonly affected, producing foot drop — an inability to lift the front of the foot — alongside numbness or tingling along the outer leg. Around half of affected patients are left with a residual deficit that may require a long-term ankle-foot orthosis, with recovery, where it occurs, typically taking ten to eighteen months. The lateral femoral cutaneous nerve carries specific risk with the direct anterior approach, sometimes causing permanent numbness over the outer thigh. Prevention centres on surgical planning: preoperative templating to avoid over-lengthening the limb, careful retractor placement, and intraoperative neuromonitoring in complex or revision cases.

How surgical approach changes the risk profile

The choice of surgical approach does not simply determine how the surgeon reaches the joint — it reshapes which risks are amplified and which are reduced.

The traditional posterior approach offers broad exposure but historically carries the highest dislocation rate, because it requires dividing the posterior capsule and external rotator tendons — the very structures that resist backward displacement of the femoral head. To compensate, it has long been paired with strict postoperative restrictions: no deep flexion, no crossing the legs. The direct anterior approach (DAA) takes a different path between muscle planes, achieving lower early dislocation rates without dividing those posterior tissues — but it introduces a different set of trade-offs: a steep learning curve associated with intraoperative femoral fractures during canal preparation, longer operative times, greater blood loss, and a meaningful risk of lateral femoral cutaneous nerve (LFCN) injury that can leave permanent numbness over the outer thigh.

No approach eliminates all four risks simultaneously. Each represents a different redistribution.

The SPAIRE technique — developed by Professor Paul Lee — occupies a distinct position in this comparison. Rather than cutting and repairing the piriformis and obturator internus, SPAIRE leaves them intact. The obturator internus crosses directly over the posterior femoral head, and its preserved tendon creates what is described as a 'strap effect': a passive viscoelastic tether and an active muscular restraint that together resist posterior dislocation — somewhat like a seat belt that is already fastened rather than one that has been cut and stitched back together. Beyond the mechanical restraint, preserving these structures maintains the muscle spindles and Golgi tendon organs embedded within them — mechanoreceptors that provide continuous proprioceptive feedback about joint position. Conventional approaches sever these, leaving the joint neurologically reliant on other signals during the critical early recovery window.

The combination of mechanical tethering and restored proprioceptive continuity is the clinical basis for removing strict postoperative hip precautions in selected patients within this technique. Dislocation outcomes in SPAIRE vary with individual anatomy, bone quality, and surgical indication, so no single figure applies universally — and the evidence base is reviewed at a patient level rather than as a population statistic. What the intact structures demonstrably provide is structural work that divided and repaired tissue cannot replicate in the immediate postoperative period. That is the honest foundation for the approach's stability claims, and it is why Professor Lee's practice centres technique selection on what the soft tissues will actually be doing after the patient leaves theatre.

Pre-operative planning: the modifiable layer

Much of what determines a hip replacement's complication profile is settled before the patient walks into the operating theatre.

Pre-operative templating is the clearest example. Using calibrated X-rays of the pelvis and femur, the surgeon plans implant size, acetabular cup angle, stem position, and expected leg length before a single incision is made. Think of it less as paperwork and more as a rehearsal: it allows the surgical team to anticipate where a press-fit stem may be tight, flag the risk of unintended limb lengthening, and verify that the planned construct will restore the hip's mechanical centre and offset. When templating identifies potential over-lengthening, it also raises a prompt about sciatic nerve traction risk — one of the documented, preventable contributors to nerve injury.

Acetabular cup positioning carries its own weight. Components placed outside the recommended range of inclination and anteversion significantly increase dislocation risk, and that risk is technique-dependent rather than fixed by anatomy — meaning it is a variable a well-prepared surgeon can act on.

Patient selection feeds into every approach decision. Bone quality, BMI, neurological history, and comorbidity burden all shape which implant system and which surgical technique is most likely to reduce complication exposure for a given individual. Surgeon experience and case volume are similarly documented influences: periprosthetic fracture risk is measurably higher during the learning curve of any unfamiliar technique, which is one reason case volume matters when choosing a surgeon.

Professor Paul Lee's biological rapid-recovery programme extends this logic beyond the operating theatre — integrating technique choice, implant selection, and mobilisation design into a single pre-planned pathway for selected patients, rather than treating the operation as a self-contained event. Recovery, on that model, is something that is designed before the surgery begins.

Questions worth raising before your operation

Armed with the detail in the preceding sections, a pre-operative consultation becomes more useful if a patient knows what to ask.

The most productive questions tend to cluster around four areas. First, which surgical approach is planned — and what about your specific anatomy, bone quality, or risk profile has shaped that choice? The answer should connect to your individual assessment, not simply to the surgeon's default preference. Second, what templating process will be used, and how will implant positioning — cup angle, stem fit, leg length — be confirmed before and during the operation? Third, which personal risk factors have been weighed: bone density, BMI, neurological history, comorbidity burden? And fourth, what postoperative precautions will you be expected to follow, and for how long? As section four made clear, the answer to that last question should differ meaningfully depending on which technique and which approach are being used.

A surgeon who has prepared thoroughly will address these points without hesitation, because they will already have worked through them in the planning process. If any go unanswered at consultation, seeking a second specialist opinion is a reasonable and legitimate step — not a confrontational one.

For patients who want to understand how approach selection, templating, and risk profiling apply to their specific situation, an assessment with a consultant who treats these as interconnected planning decisions rather than separate boxes to tick is likely to produce a more useful conversation.