Abstract
Background
Sciatic nerve palsy is a relatively rare, but one of the serious complications after total hip arthroplasty (THA). The prevalence of nerve palsy after THA has been reported to range from 0.3% to 3.7%. Previous authors have speculated that causes could include overlengthening, compression from a hematoma, from extruded metylmethacrylate, or from retractor placement, or laceration from a screw used in the acetabular component. Leg lengthening more than 4 cm was associated with sciatic nerve palsy in the past literature. But there is no report about maximum safety leg lengthening to prevent sciatic nerve palsy significantly. The purpose of this study was to identify the safety rage of leg lengthening to prevent sciatic nerve palsy in THA for the patients with adult hip dislocation.
Methods
Forty two consecutive patients47 jointswith Crowe type â?¢ or â?£ were performed THA. Nine joints were Crowe type â?¢ and thirty eight joints were type â?£ in this study.
All patients were female. The average age at the time of surgery was 63.3 years (range, 40–77 years). The average patient body weight was 50.5 kg and the average height was 150 cm (body mass index: 22.3 kg/m2). The average follow-up was 9.9 years (range, 1–21). See Table1 The socket was placed at the level of the original acetabulum, and femoral shortening osteotomy was performed in 27 joints. Leg lengthening (LL) was defined the vertical distance from the tip of greater trochanter to the tear drop line. The mean LL was 3.1 cm (range, 1.5–6.7 cm). Clinical Harris hip score and sciatic nerve palsy was retrospectively assessed from the patients records. The correlation between LL, the percent LL (cm) divided by body height (cm) (%LL/BH) and the incidence of sciatic nerve palsy was investigated.
Results
There were two sciatic nerve palsy (4.3%). These leg lengthening were 5.2 cm and 6.7 cm, respectively. These patients had complete recovery of neurological function. A significant correlation between the amount of LL and the incidence of sciatic nerve palsy was identified. LL more than 5 cm and %LL/BH â?§ 3.6 were significant risk factors of sciatic nerve palsy (p=0.0194, p=0.0028). See table2.3 Body mass index, preoperative hip flexion, previous operations were not associated with sciatic nerve palsy.
Harris hip scores improved from a mean of 57.6 points prior to surgery to an average of 83.1 points at the latest follow-up. Kaplan- Meier survivorship analysis at 5 and 10 years revealed a cumulative survival rate of 94.1% and 64.2% respectively, with any implant revision as the end point. There were six cases of dislocations, which were successfully treated conservatively. Infection was not observed.
Conclusions
Leg lengthening more than 5 cm and %LL/BH â?§ 3.6 were significant risk factors of sciatic nerve palsy.
