Introduction

Total hip arthroplasty (THA) is considered the golden standard in treating severe, symptomatic osteoarthritis of the hip, should the conservative treatment fail to provide satisfactory pain relief [1]. Since the introduction of low-friction arthroplasty by Charnley, numerous approaches have been developed and adapted for hip joint replacement [2]. The most commonly utilized methods include posterior and lateral approaches [3]. The lateral approach (or direct lateral approach) has been proven to have a lower dislocation rate compared to the posterior approach. However, it is associated with abductor muscle weakness (positive Trendelenburg sign) [4]. New, minimally invasive approaches have been introduced to overcome these shortcomings.
Direct superior approach (DSA) is one of the minimally invasive approaches to the hip joint, developed as a modification of the standard posterior approach, in which the iliotibial band, obturator externus and quadratus femoris muscle are spared [5]. Performing posterior repair (piriformis and conjoined tendon, joint capsule) leads to decreased dislocation rate compared with the traditional posterior approach [6]. Specialized surgical tools are required to facilitate adequate visualization, acetabular reaming and femur preparation, and implant delivery [5]. Less extensive soft tissue damage is hypothesized to cause less pain in the early postoperative period and shorten the length of hospitalization.

Aim of the study

The hypothesis was adopted that less extensive soft tissue damage will cause less pain in the early postoperative period and allow to reduce the use of analgesics compared to the direct lateral approach. Moreover, despite a more demanding surgical technique and worse visualization of the hip joint, it predicted similar long-term results in terms of quality of life, pain intensity, dislocations, and overall revision rate.

Materials and methods

Sixty-one consecutive patients scheduled for THA were recruited for the study. Inclusion criteria were as follows: primary hip osteoarthritis, no concomitant, severe degenerative changes in the lumbar spine. Exclusion criteria were: secondary hip arthritis (rheumatoid arthritis, avascular necrosis of the femur head , post-traumatic osteoarthritis, and developmental dysplasia of the hip).
The following data was collected on the day preceding surgery: age, gender, body mass index (BMI), comorbidities, pain intensity in Numerical Rating Scale (NRS), Harris Hip Score (HHS), and Short Form Health Survey (SF-36).
Surgery was performed by experienced orthopedic surgeons (over 50 THAs annually). The choice of approach was based on the surgeon’s preference and expertise.
Pain intensity was recorded multiple times on the first, second- and third-day following surgery according to hospital protocol. Analgesic drugs were assessed and used according to WHO Analgesic Ladder and institutional pain management protocol. Patients were discharged on the third day following surgery.
After 18 months, patients were contacted via phone, and the following data was collected: patients’ overall satisfaction (from 1-5 Likert scale), pain intensity in NRS, quality of life (SF-36), and complications (dislocations, periprosthetic fractures, periprosthetic joint infections, implant loosening).
With 9 patients lost to follow-up, 52 participants were included in the final analysis. Grup A (DSA) consisted of 27 patients, while group B (lateral approach) consisted of 25 patients.
Statistical analysis was performed by a biostatistician using PQStat software. Mann-Whitney test was used for non-normal distribution interval independent variables, whereas t-Student test was utilized for normal distribution interval independent variables. Statistical significance was set at p < 0.05.

Results

No differences were observed in the study group in terms of age (62.2 vs 65.2, p = 0.28), gender and BMI (28.5 vs 29.3, p = 0.77). The study cohort was homogeneous in terms of HHS (41.9 vs 46.6, p = 0.24), GAD-7 (8.9 vs 8.8, p = 0.96) and SF-36 (109.4 vs 103.1, p = 0.39). No significant difference was shown in preoperative pain intensity (7 vs 7, p = 0.43) (Table 1).
During postoperative measurements of pain intensity, significant divergence was observed between study groups. In group A, patients experienced less intense pain than group B. This difference was shown in the first (2 vs 3, p = 0.006), second (2 vs 3, p = 0.00003) and third day (2 vs 3, p = 0.007) following surgery. Interestingly, the use of tramadol was lower in group A on the first and second day (50 mg vas 100 mg, p = 0.008, 0 mg vs 100 mg, p = 0.004). However, no significant difference was observed on the third day (Table 2).
At the follow-up after 18 months, both groups presented satisfactory results in terms of pain intensity in NRS (1 vs 1, p = 0.54), SF-36 (42 vs 49, p = 0.36) and overall satisfaction (5 vs 5, p = 0.54) (Table 3). No complications such as dislocations, periprosthetic fractures, periprosthetic joint infections, implant loosening, or revision surgeries were reported.
Discussion

Total hip arthroplasty is one of the most desirable and successful procedures in orthopedic surgery [7,8]. In Poland, over 59 000 THAs were performed in 2022 [9]. Due to the aging population, the number of procedures is expected to increase further [10]. While long-term results are mainly influenced by proper implant positioning to achieve optimal stability and range of motion, patient satisfaction is a multifactorial issue [8,11,12]. To reduce early postoperative pain, decrease the length of hospitalization and improve recovery, new, minimally invasive approaches were introduced: direct anterior approach (DAA) and direct superior approach (DSA) [5,13]. The iliotibial band-sparing approaches are believed to accelerate recovery and decrease the use of pain medication [14]. The direct superior approach is considered more versatile and adaptable than the direct anterior approach due to the relative absence of a learning curve and possibility of extending the cut to transform it into a posterior approach if necessary [5,15]. Moreover, dislocation revision rate in patients who underwent DSA-THA has been reported to be comparable to DAA [6].
This study compared early and long-term results of DSA-THA with lateral approach THA. Despite the vast literature on THA approaches, no studies have been found that compare the DSA and lateral approaches. Current evidence seems to favor iliotibial band-sparing approaches in terms of postoperative pain, recovery and hospitalization time, while denying long-term benefits, as long as no major complications arise [16–18]. In this study, patients undergoing DSA-THA experienced less intense postoperative pain and required less opioid drugs than patients undergoing lateral approach THA. This observation seems to be supported by current literature. The key to understanding this correlation seems to be the undamaged iliotibial band [14]. Interestingly, minimally invasive approaches that violate the iliotibial band seem to have little or no advantage compared to traditional approaches [16,19].
As demonstrated in previous studies, the iliotibial band-sparing minimally invasive approaches in THA produce better early results, yet no long-term advantage has been proven. In this study, both groups presented excellent functional results, pain levels and satisfaction rates after 18 months following surgery. Such observation may indicate that DSA-THA is non-inferior in terms of long-term results and does not compromise implant positioning. No major complications were recorded, which could be attributed to the relatively small study cohort. However, complications after THA are relatively rare. At the authors’ institution, periprosthetic joint infection rate is below 1%, which is supported by the literature [20]. Revisions due to dislocation occur in 0,3% of cases after DSA and 0,4% for direct lateral approach [6,21]. Those factors may have contributed to the lack of major complications in the study cohort.
The study had several limitations, the primary one being the small sample size. Moreover, the results may have been influenced by the relatively high percentage of patients lost to follow-up (14%). Due to the lack of randomization, the results may have been impacted by applying a more suitable (i.e., technically less demanding) approach in patients with certain characteristics (e.g., obese). Patients informed about the minimally invasive approach could have been influenced by that fact and perceived postoperative pain as less intense.
Despite the above limitations, this study is the first, to the authors’ knowledge, to compare the direct superior approach with the direct lateral approach in hip arthroplasty.

Conclusions

The DSA approach in THA is superior in comparison with the direct lateral approach in terms of early postoperative pain intensity and use of tramadol. Late results of both approaches are comparable. It is also a valuable alternative to the traditional direct lateral approach. Further studies with larger cohorts are required to explore this issue.

References

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