The use of a modified posterior approach (SPAIRE) may be associated with an increase in return to pre-injury level of mobility compared to a standard lateral approach in hemiarthroplasty for displaced intracapsular hip fractures: a single-centre study of the first 285 cases over a period of 3.5 years

Displaced intracapsular hip fracture patients are treated with arthroplasty, most frequently being a hemiarthroplasty [1]. Mobility and functional independence have been reported to be the main priority for hip fracture patients [2].

The National Institute for Health and Care Excellence (NICE) from the United Kingdom recommends that surgeons consider the lateral in favour of the posterior approach when inserting a hemiarthroplasty, but acknowledges that evidence for this recommendation is of very poor quality, being based on only two studies [3‐5].

Evidence from an observational study from the Norwegian Hip Fracture Register of over 20,000 patients suggests better patient-related outcome measures of pain, patient satisfaction and health-related quality of life with the standard posterior approach when compared with the lateral approach although the recorded dislocation rate was much higher in the posterior approach group [6]. Dislocation, although relatively rare can lead to catastrophic consequences in this frail cohort of patients [7‐9].

In this paper we describe a reproducible tendon-sparing modification of the posterior approach using the muscle interval between gemellus inferior and quadratus femoris leaving the insertions of gemellus inferior, obturator internus, gemellus superior and piriformis intact—the SPAIRE technique (acronym for “Saving Piriformis And Internus, Repair of Externus”). This has been adopted by the surgeons at our specialist hip unit when performing hip hemiarthroplasty for displaced intracapsular fractures. In 2020, the SPAIRE technique was also adopted in 5.7% of all hemiarthroplasties performed in Norway, as shown in the 2021 annual report of the Norwegian hip fracture database [10].

The aim of this article is to report on details of the SPAIRE technique with results on the first 285 hemiarthroplasty cases performed at our unit, comparing return to pre-injury level of mobility of these patients at 120 days post-admission with that of hemiarthroplasty patients operated on over the same period for whom the standard lateral approach was used.

Data were obtained from the NHFD that included a telephone follow-up at 120 days, and we searched our hospital electronic patient record system for all patients undergoing hip hemiarthroplasty between 28 September 2016 and 31 March 2020. We recorded return to pre-injury level of mobility at 120 days post-admission (routinely recorded on the NHFD database as one of the following categorical variables: “freely mobile without aids”, “mobile outdoors with one aid”, “mobile outdoors with two aids or frame”, “some indoor mobility but never goes outside without help”, and “no functional mobility”), length of stay, pre- and post-operative place of residence, complications requiring re-operations including closed manipulation of dislocated joints and mortality within 120 days. One hundred and twenty-day follow-up rates recorded on the NHFD for our hospital (for all hip fracture types) were over 97% over the 4-year study period (97.1% in 2019, 98% in 2018, 97.9% in 2017 and 99.3% in 2016).

285 cases using the SPAIRE technique were performed from 28 September 2016 to 31 March 2020. In the same period, 567 cases using the lateral approach were performed by all surgeons involved with trauma care at our department. 3 cases performed by a single surgeon using a modified posterior approach in which obturator internus was deliberately divided but piriformis preserved, were excluded from the analyses presented in this paper. Only 1 patient could not be contacted at 120 days so was lost to follow-up.

Table 1 summarises the population demographics.

Table 2 describes the two surgical approach groups in terms of the level of surgeon seniority present during surgery and the type of implant used. A cemented Exeter stem was used in every case in this cohort, being either a monoblock Exeter Trauma Stem (ETS—Stryker Corporation, Kalamazoo, Michigan, USA) or a bipolar modular construct using the Exeter V40 stem with an Orthinox stainless steel head in a Universal Head Bipolar System (UHR) bipolar head component (Stryker Corporation, Kalamazoo, Michigan, USA).

Table 3 shows results of analyses comparing the outcomes measured between SPAIRE and lateral approaches. Data on 120-day level of mobility were available for 252 of the 285 (88.4%) SPAIRE and 460 of the 567 (81.1%) lateral procedures. The odds of returning to pre-injury level of mobility were higher in the SPAIRE group than in the lateral group, adjusted OR (95% CI) 1.7 (1.1 to 2.7), p = 0.01. Survival within 120 days was improved in the SPAIRE group, compared to the lateral group, adjusted HR for mortality (95% CI) 0.6 (0.4 to 0.9), p = 0.02. There was little evidence of an effect of surgical approach on other outcomes measured.

Complications requiring re-operations in the entire series included 3 peri-prosthetic fractures (0.4%—2 cases from the lateral group treated with open reduction and internal fixation and 1 case from the SPAIRE group treated with revision of the femoral component). There were 3 peri-prosthetic infections (0.4%—1 case from the lateral group treated with washout and debridement only, 1 case from the lateral group treated with debridement and implant retention and 1 case from the SPAIRE group treated with Girdlestone excision arthroplasty). 4 dislocations (4 patients) occurred in the whole cohort (0.5%—3 cases from the lateral group (0.5%) treated with conversion to total hip replacement and 1 case from the SPAIRE group (0.4%) treated with closed manipulation under anaesthetic and no recurrence). There was 1 traumatic wound dehiscence in a case from the lateral group treated with washout and closure. There were no cases of nerve palsy.

In 2012, Han et al. reported a reduced incidence of dislocation using a minimally invasive posterior approach in patients suffering a neurological disorder. The authors described a modification by which piriformis, gemellus superior and obturator internus were left intact [7]. In their description, a conventional capsule repair was carried out prior to closure. Modifications in surgical technique have been previously attempted to improve joint stability after hemiarthroplasty in patients at increased risk as a result of a specific comorbidity [14]. The SPAIRE technique for total hip arthroplasty was reported by Hanly et al. [15].

The SPAIRE technique in hip hemiarthroplasty was first performed on 28 September 2016 by the senior author. An initial report on the first 25 hemiarthroplasty cases using the SPAIRE technique at our institution suggested the technique was feasible and safe to be used [16].

In a cadaveric study, Vaarbakken et al. demonstrated the importance of the short external rotators (namely the piriformis, gemellus superior, obturator internus and gemellus inferior muscles) in hip function, acting as the main extensor and abductor muscle group of the flexed hip (i.e. when the hip is in a flexed position of up to 90°). This is of particularly significant importance for movements such as rising from a chair and climbing stairs. The same authors named these four muscles quadriceps coxa due to their synergistic action on movements of the hip and for attaching as a same group onto the greater trochanter [17]. By preserving these important muscles along with gluteus medius and minimus, the SPAIRE technique may facilitate better recovery in hemiarthroplasty patients. This contrasts with the standard lateral approach, where a significant proportion of the largest muscle group of the hip, gluteus medius and minimus are split or divided, potentially impacting on hip function. We believe the combination of this muscle sparing approach with an enhanced capsular repair at the end of the procedure provide sufficient stability to enable patients to fully weight bear and mobilise with no restrictions whatsoever after surgery, the same as for the standard lateral approach. By preserving the short external rotators along with a posterior repair that includes capsule and obturator externus, the SPAIRE technique may reduce the dislocation rate associated with the standard posterior approach whilst potentially improving functional outcomes for this frail group of patients. The experience of our hip unit with this tendon-preserving technique has been positive, and although objective measurements have not been possible in this retrospective study, we have not observed an increase in surgical time or blood loss when compared to the standard lateral approach.

This report has limitations. It is an observational study of only 852 cases. Although the patient population in this study may not be large enough to capture significant differences between each group for rare events such as dislocation, infection or neurovascular injury, the single episode of a traumatic dislocation in the SPAIRE group (0.4%) versus three non-traumatic dislocation episodes in the lateral approach group (0.5%) and no reported neurovascular injury are reassuring findings and do not raise concerns of possible harm to patients associated with this new technique. While the majority of operations across both series were carried out in the presence of consultant level surgeons, the SPAIRE group comprised of hip subspecialty consultant level presence in 88.8% of cases, in contrast to involvement of consultant level from all orthopaedic subspecialties (including hip) in the lateral group in 82.9% of cases. Being a modification of the posterior approach, the SPAIRE technique is more likely to be adopted initially by hip subspecialty surgeons who are more familiar with that approach. However, specialist hip consultant level presence at surgery in the SPAIRE group is unlikely to explain the improved rates of return to pre-injury level of mobility and mortality observed in that group. No patients were selected for referral to the hip team; patients had their operations under the care of the orthopaedic consultant on-call, usually on the first available list after their admission as recommended by NICE guidance on hip fracture care [3]. A higher proportion of constructs using modular stems with a bipolar head were used in the SPAIRE group (44.9% vs. 22.6% in the lateral group). This construct is used in preference to a monoblock stem by the hip unit specialist surgeons to match individual patient anatomy in situations when it is felt that a monoblock stem will not meet this requirement. However, neither stem modularity nor the use of a bipolar head construct are likely to explain the improved rates of return to pre-injury level of mobility and mortality observed in the SPAIRE group. There is no evidence in the literature that either of these improve mobility or mortality rates in hip hemiarthroplasty patients within 120 days [18‐20]. The SPAIRE approach has significantly better clinical outcomes than the lateral approach in this study. However, this is not to say that the SPAIRE approach is superior to the conventional posterior approach with regards to function. A comparison of the SPAIRE approach with the conventional posterior approach was not possible in this retrospective cohort as not used at our department.

Following the recommended stages of surgical innovation of the IDEAL framework a multicentre randomised controlled trial sponsored by our institution and funded by the National Institute for Health Research (NIHR) is under way [21]. Currently in its recruitment phase, the HemiSPAIRE study aims to compare the SPAIRE and the standard lateral approaches in hip hemiarthroplasty with regards to function.

When treating displaced intracapsular fracture patients with hip hemiarthroplasty, the SPAIRE approach appears safe and may provide not only joint stability but also superior functional recovery, as demonstrated by an increase in return to pre-injury level of mobility compared to that of a standard lateral approach. However, further research is required to conclude any potential benefits. The SPAIRE technique is routinely used for hemiarthroplasty by all hip specialist surgeons and trainees at our unit.