We performed the BHA using a novel method, the CPP approach, in geriatric patients aged ≥ 80 years. Making the capsule incision between the gemellus inferior and external obturator muscles allowed us to preserve the conjoined tendons except for that of the external obturator muscle, in almost all the patients.
The aging of society has led to more opportunities for performing BHA in geriatric patients. It can be difficult to instruct these patients on how to prevent dislocations due to their lack of understanding of limb positions that may cause dislocation. As hospital stays need to be shortened to reduce medical costs, there is a need for surgical methods that prevent dislocation because of daily activities, excluding falls and other accidents.
The most common conventional posterior approach involves incising the capsule and short external rotator muscles separately. Recently, methods have been employed that incise the capsule and short external rotator muscles together instead of separately, or only preserving the piriformis muscle. The short external rotator muscles and capsule play an important role in preventing hip dislocation. The short external rotator muscles and ischiofemoral ligament provide dynamic stability by controlling internal rotation, and the capsule provides static stability by acting as a posterior wall, both of which prevent dislocation. However, once the capsule and short external rotator muscles are cut, they have been found to re-rupture postoperatively at high rates of 75–92%, even after being repaired [14, 15]. Han et al. performed BHA using ERP in femoral neck fracture patients with mental disorder [4]. They reported that compared with the conventional posterior approach, there were no differences in operation time and bleeding, however, the rate of postoperative dislocation was significantly lower.
The CPP approach preserves from the piriformis muscle to the gemellus inferior muscle. Because this approach preserves the gemellus inferior muscle, we consider that this approach is superior to ERP at preventing postoperative dislocation. Moreover, the subjects in the present study were all geriatric patients aged ≥ 80 years who may have had soft tissue fragility. In this study, the gemellus inferior muscle was difficult to identify in 2 cases and muscle-tendon damage was observed in 4 cases. The Alloclassic-SL™ system was used in the 4 patients with gemellus inferior muscle damage. These muscles are thought to have been damaged by the shoulder of the stem during rasping. Therefore, when using this approach, it is recommended to use a taper wedge type stem with reduced stem shoulder. That being said, due to individual differences in the shape of the conjoined tendon and external obturator muscle insertion sites, some degree of gemellus inferior muscle damage during rasping may be unavoidable. However, hip joint stability was very excellent in all cases and there were no cases of postoperative dislocation. The 4 cases with gemellus inferior muscle damage were highly resistant to posterior dislocation owing to the intact posterior capsule and ischiofemoral ligament, which indicates the CPP approach is useful in geriatric patients. The Sparing Piriformis muscle and Internus, Repair Externus (SPAIRE) technique is a muscle sparing mini-posterior approach for the THA reported by Handy et al. [16]. This approach enables preservation of the piriformis muscle tendon and conjoined insertion of obturator internus and the gemelli. However, a posterior capsulotomy is performed in an L-shape with a proximal oblique limb (at 10 o’clock for right hip, 2 o’clock for left hip) starting subjacent to the preserved quadriceps coxae tendons [16]. Therefore, this approach has 2 shortcomings. The first is the lower resistance to posterior dislocation from the posterior capsule than the CPP approach. The second is that due to the lack of a posterior capsule and the exposed conjoined tendon, the gemellus inferior muscle is more likely to be damaged than with the CPP approach.
Many young and inexperienced surgeons perform BHA for femoral neck fractures. Although the posterior approach is technically simple and provides a good field of view, we believe that the BHA with the CPP approach would be easy to adopt for surgeons with some experience with the posterior approach, because this approach needs no specialized equipment. While there is a surgical related learning curve, the operation time is less than 1 hour and if the surgical technique proves difficult the surgeon can switch to the conventional posterior approach. The CPP approach, which is highly resistant to posterior dislocation, can be considered a highly useful method for femoral neck fractures that accompany aging.
However, this study had a limitation and weaknesses. The sample size of the current study was relatively small to evaluate the outcomes of CPP approach. To validate our findings, future studies with larger sample sizes will be required.
In conclusion, we attempted to preserve the short external rotator muscles in BHA using the CPP approach in geriatric patients with soft tissue fragility. There were no intraoperative problems or postoperative dislocations, indicating that the CPP approach is useful for geriatric patients as well.