The Pavlik sling method was first proposed by Arnold Pavlik in 1944. By keeping the child in a flexed hip and knee position with natural abduction, the dislocated hip joint can be dynamically and safely repositioned with a high success rate of repositioning and a low incidence of complications such as Avascular Necrosis (AVN). The core concepts are: 1) the femoral head is movable compared to the acetabulum; 2) greater abduction angle with hip flexion and knee flexion; 3) more stable reset with hip flexion and knee flexion; 4) natural abduction by its own gravity. The process of repositioning by Pavlik sling can be divided into two steps: 1) flexion of the hip and knee to make the femoral head touch the posterior aspect of the acetabulum, which may lead to failure of repositioning if the glenoid lip is not crossed; 2) abduction to make the adductor muscle tense, with the femoral head – the posterior wall of the acetabulum as the fulcrum, the adductor muscle, mainly the pubococcygeus muscle, short adductor muscle and short head of the greater adductor muscle, produces the mechanical vector of pulling the femoral head upward and inward (pointing to the acetabulum), gradually achieving dynamic The resumption is gradually achieved. Indications Dysplasia, subluxation, dislocation in infants aged 0-6 months. Contraindications The Pavlik sling is used with caution in the presence of various neuromuscular disorders such as muscle imbalance (e.g. spina bifida), stiffness (joint contracture), joint laxity (Ehler-Danlos syndrome), etc. The Pavlik sling is based on the premise that the hip-related muscles are normal. Treatment principles Treatment should be started immediately upon diagnosis, and a review plan should be made according to clinical stability. Simple dysplasia (Barlow): review ultrasound every 6 weeks for clinical stability and stop wearing it if ultrasound or X-ray (more than 5 months) results are normal after 3 months of wear. Unstable clinical examination (Barlow+): repeat ultrasound every week, repeat ultrasound every 6 weeks after stabilization, stop wearing if X-ray results are normal after 3 months of wear. Dislocation (Ortolani+/): repeat ultrasound weekly, stop treatment after 3 weeks if not reset and switch to other modalities. If successful repositioning is repeated as in Barlow+ patients. Wearing method The Pavlik sling consists of three parts, the body (including chest and shoulder straps), the left leg and the right leg. The child is placed in a quiet supine position. The chest strap is placed just below the nipple line, the shoulder straps are crossed over the scapulae and around the shoulders and tied to the chest button, and finally the left and right leg slings are worn separately, with the proximal nylon buckle of the leg placed below the N-fossa and the distal nylon buckle placed about 3 cm above the ankle joint. To connect the body and leg parts, the anterior connecting strap is adjusted to maintain the hip joint flexion at 90-110°, and the posterior connecting strap is adjusted in the prone position to limit Adjusting the posterior attachment strap in the prone position is sufficient to limit hip inversion. Return to the supine position and check hip abduction and adduction. Adduction is obtained by the child’s lower limb dropping by its own gravity, and the posterior band should be kept loose to restrict hip adduction without causing abduction. After wearing the sling, the sling should be adjusted by specialized personnel every 2~3 weeks on average according to the growth of the child. Technical points The chest belt is located below the nipple line, too low will affect the abdominal breathing. The shoulder straps are crossed at the back to prevent them from slipping off to both sides. The distal and proximal calf straps are located below 3cm N fossa above the ankle joint respectively, fixing the full length of the calf, avoiding external rotation of the calf and achieving full hip flexion. The anterior connecting straps of the body and leg are placed at the anterior axillary line to avoid producing external rotation of the hip joint, while the calf portion of the anterior strap is located on the medial side of the calf to avoid causing internal rotation of the hip joint at the front due to slippage. The hip was maintained at 90-110° of flexion, with natural abduction caused by the gravity of the lower limb, usually 50-60°, to avoid complications such as AVN and femoral nerve palsy due to excessive hip flexion and abduction. Treatment outcomes Short-term outcomes Pavlik himself reported a success rate of 84.08% for early treatment of hip dislocation in the Pavlik sling. Subsequent success rates reported in the literature for hip dislocation treated with Pavlik slings ranged from 61% to 95%, and 94% to 99% for subluxated or dislocatable hips. 89.7% of 547 cases of hip dislocation treated with Pavlik slings were successfully repositioned within 2 weeks, 8.3% at week 3, and 2% at week 4, as reported by Malkawi. Grill et al. reported the results of early treatment of 3611 hips with Pavlik sling in 2636 patients with DDH, and the success rates of repositioning were 95%, 96%, 83% and 80% for Tonnis classification 1~4, respectively. The success rate was stable at about 81%. Intermediate results Grill et al. showed that the AVN incidence was 2.38% at 1-9 years of follow-up, with the incidence of AVN in cases less than 3 months reduced by half compared with cases over 3 months, and the incidence of AVN in Tonnis classification 1-4 was 1.28%, 2.12%, 3.1% and 16.4%, respectively. Harris et al. showed 5% residual dysplasia in 550 patients with DDH at 2 years of follow-up. Long-term results Some studies showed that 66.7%-83% of final clinical and imaging results were excellent 12-24 years after Pavlik sling treatment.Takao et al. followed up DDH cases treated with Pavlik sling for at least 14 years and showed that 71.9% had excellent final Severin results, 28.1% had moderately poor results, and 10% had AVN, and concluded that OE at 3 years of age angle (CE angle centered on the midpoint of the proximal femoral epiphysis) less than 2° predicts poor long-term outcome. Problems and complications Reset failure About 10-15% of cases of dislocation have reset failure. Factors associated with reset failure in Pavlik slings for hip dislocation are mainly related to age at treatment, unilateral and bilateral, degree of dislocation, and clinical Ortolani examination, and remain somewhat controversial. There are also cases of successful repositioning but failure to maintain stable repositioning, which may be related to ligamentous laxity or the presence of factors blocking repositioning. Femoral nerve palsy presents with an inability to actively straighten the knee joint in the affected lower extremity and no significant kicking response to stimulation of the plantar aspect of the foot. The incidence of femoral nerve palsy has been reported to be 2.5%. If the sling is removed promptly, the symptoms can be relieved and disappear within a few weeks. Excessive hip flexion causing femoral nerve strain is the main causative factor, and obesity and severe hip abduction restriction may be risk factors. Femoral head necrosis (AVN) The most serious complication, with an incidence of 0-30%, is mainly related to the initial age of treatment and severity of dislocation. Irregular sling wearing Improper sling wearing, inappropriate sling size and lack of standard review may lead to various complications. Failure to effectively restrict internal retraction may lead to reset failure and posterior wall resorption. Excessive hip flexion may lead to femoral nerve palsy or subclavian dislocation. Excessive abduction is more conducive to repositioning and stabilization, but may increase the risk of AVN. Parental compliance During treatment, parental compliance, including regular review, adherence to treatment and careful care, is also associated with the outcome of sling treatment and the occurrence of complications.