Risk of dislocation during childbirth after total hip arthroplasty: a systematic literature review

Discussion To date, a growing number of fertile patients undergo THA. Although the implants and surgical technique has improved gradually over the years, dislocation is still a frequently encountered complication following THA surgery. Pregnant patients might be more prone to dislocate their THA due to additional risk factors, such as the release of relaxin which increases ligament laxity to ensure successful vaginal delivery and enlarged axial stressful forces placed on the axial and pelvic region due to the altered maternal centre of gravity. In this systematic review we aimed to evaluate the risk of dislocation during pregnancy and childbirth after THA. In the studies included, only 1 out of 312 births has led to a dislocation. The patient who suffered a dislocation underwent a caesarean section. This study should be interpreted in the light of its limitations. Three articles did not specifically report the number of dislocations14,19, 20. However, these articles stated that there were no (other) complications. Based on this statement we assumed there were no dislocations in these studies. Secondly, most studies had a small sample size. This increases the likelihood of a type II error skewing the results. Furthermore, there was a large variety in the aim and objectives of the included studies. Leading to no uniformity in reported outcomes and metrics used. Moreover, most studies were of retrospective design. Despite these limitations, we believe the results of this review are a valuable contribution to current knowledge on the risk of dislocation during pregnancy and childbirth in THA patients. The majority of studies reported a percentage between 50-70% for vaginal deliveries and between 30-50% for caesarean sections8,14-17,19,20. However, higher percentages for caesarean deliveries were reported in the studies of Kuitunen et al. (56%) and Stea et al. (95%)18,21. The higher number in the latter study might be due to an overall higher number of caesarean sections done in Italy and due to the higher percentage of developmental dysplasia of the hip (DDH) in their study population. In general, DDH does not alter the inner border and shape of the pelvis and does not influence the need for a caesarean section. In addition, surgery for DDH during early childhood does not change the size of the pelvis (e.g., open reduction, proximal femur osteotomy) and surgery before the age of six (Pemberton osteotomy) does not cause difficulties during pregnancy later in live due to the large remodelling capacity of the pelvis. However, DDH patients can have a reduced inner pelvic size after bilateral pelvic surgery (Steel, Chiari, Sutherland, and Salter osteotomy) and this can have an effect on the mode of delivery18,23. The effect of the underlying disease that led to THA surgery should be taken into account. Literature demonstrates a higher risk of dislocation in patients with avascular necrosis, a hip fracture, or inflammatory arthritis as indication for THA compared to osteoarthritis24. In our study the most common indications for THA surgery were inflammatory arthritis, DDH, avascular necrosis, and hip fractures. This means that this specific patient group is a priori more prone to dislocations. However, only one patient suffered a dislocation indicating that even with an increased risk due to the underlying disease the absolute risk is still low for dislocation. The only patient that suffered a dislocation gave birth via a caesarean section. During caesarean sections regional anaesthesia is used in the majority of cases and seldom general anaesthesia. Regional anaesthesia needs to give a(n) (almost) complete motor block and thus the patient has a decreased sensibility and motor control in the lower part of her body25. Therefore, the position of the hip could not be controlled by the patient and should be actively monitored by the healthcare providers during the delivery. This could possibly have aided in dislocating the hip. However, in some countries regional anaesthesia is also frequently administered during vaginal deliveries. Nonetheless, a lower dosage is used, since the motor block needs to be minimized to preserve the ability to push during vaginal delivery26. The patient thus has more sensibility and motor control on the lower body compared to regional anaesthesia given for a caesarean section. Furthermore, the time between THA surgery and the risk for dislocation is of importance. It is known that the highest probability of dislocation occurs within the first months after surgery27. Woo and Morrey stated that 59% of the dislocations occurred within the first three months after THA surgery and 77% within the first year28. Berry et al. showed that 21% of the dislocations occurred within the first 31 days and 38% in the first year after THA surgery24. In our data, the mean time of THA implantation to pregnancy was 26.4 (range 2-128.4) months. Only one patient became pregnant within the first year after surgery11 while the other patients became pregnant at least twelve months after THA and only one suffered a dislocation. This implicates THA is not performed in pregnant patients and consequently, the period of delivery will be after the period of increased risk for dislocation. Other risk factors for dislocation which have been identified are implant orientation and surgical technique (both approach, femoral head diameter, and surgical skills). Arthroplasty registry data shows that the risk for revision for dislocation is acceptably low in The Netherlands (around 1%)29. Based on the results of the studies included in this systematic review, no association between the surgical approach and the risk for dislocation during pregnancy and childbirth was found. Conclusion This systematic review of literature suggests that there is no increased risk of dislocation during pregnancy and childbirth in THA patients. Only one patient suffered a dislocation during childbirth in 312 deliveries. This patient gave birth via a caesarean section. Thus, zero patients who gave birth vaginally suffered a dislocation during childbirth. No evident risk factors for dislocation during pregnancy could be identified. However, we posit that the position of the hip during childbirth is important. Further studies regarding the risk of THA dislocation during pregnancy and childbirth should ideally be prospective with large patient numbers.

Disclosure statement Authors have no conflict of interest to declare.