Malalignment and distal contact of short tapered stems could be associated with postoperative thigh pain in primary total hip arthroplasty

Abstract

Purpose: Short tapered stem placement has been extensively employed in total hip arthroplasty (THA). Suboptimal fixation tends to cause postoperative complications, such as thigh pain. However, it remains unclear whether poor seating/alignment of short tapered stems contributes to thigh pain. In this study, we retrospectively examined the factors that might be associated with thigh pain.

Methods: Medical records of 230 patients who had undergone THAs at our hospital were reviewed retrospectively. All patients received the same mediolateral (ML) short tapered femoral stems. The association between thigh pain and patients' demographics, radiographic findings, or the type of fitting of the femoral stems was investigated.

Results: In our cohort, 68 patients (27.8%) presented with thigh pain. Among 203 type I fit patients, 62 (30.5%) developed thigh pain, while only 6 out of 43 (12.2%) type II fit patients had thigh pain, with the differences being statistically significant (x² = 6.706, p = 0.01). In addition, hip anteroposterior radiographs exhibited that the stem angulation (mean 2.52°), the variation in angulation (mean 1.32°), and the extent of femoral stem subsidence (mean 0.29 cm) were greater in patients with thigh pain than in their counterparts without thigh pain (all p < 0.05).

Conclusion: Malalignment and improper seating of short tapered stems could be at least one of the reasons for post-THA thigh pain. The distal contact between the stem tip and the medial femoral cortex might result in thigh pain. Our study suggested that distal implant contact should be avoided, and stem alignment should be meticulously performed in the placement of ML short tapered femoral stems for THA.

Keywords: Distal contact; Short tapered stem; Stem malalignment; Thigh pain; Total hip arthroplasty.

Fig. 1

a–c A representative image for type II fit. This patient was a 66-year-old woman who underwent THA at age 65 using a short tapered stem. a A preoperative AP radiograph of her left hip. b A 6-month postoperative AP radiograph of the hip. c A 6-month postoperative lateral radiograph of the hip. The following parameters were measured: (d) metaphyseal diameter 2 cm above the level of the lesser trochanter midpoint, (e) isthmus diameter which represents the width of the narrowest part of the proximal femoral canal, (f) diameter of the femoral shaft which is measured 10 cm distal to the center of the small trochanter, (g) internal width of the medullar canal which is measured 10 cm distal to the center of the small trochanter, (h) width of the stem which is measured at the proximal end of stem tip arc, (i) internal width of the medullar canal which is measured at the proximal end of the tip arc, (j) width of the stem which is measured at the distal end of porous coating, and (k) internal width of the medullar canal which is measured at the distal end of porous coating

Fig. 2

a–c A representative image for type I fit. This patient was a 62-year-old woman who underwent THA at age 60 using a short tapered stem, which is a type I fit. a A postoperative AP radiograph of her left hip. b A postoperative lateral radiograph of the hip. C A 6-month postoperative AP radiograph. The following parameters were measured: (α₁) CSA, which represents the angle between the stem axis and the femur axis at the first follow-up; (α₂) CSA, which represents the angle between the stem axis and the femur axis at the last follow-up; (s₁) distance between the major trochanter apex and the stem shoulder perpendicular to the femoral stem axis at the first follow-up; (s₂) distance between the major trochanter apex and the stem shoulder perpendicular to the femoral stem axis at the last follow-up; and (β) SSA, which represents the angle between the stem axis and femur axis at the first follow-up. In the AP radiograph, if α₁/α₂ > 0, it illustrates the stem alignment is valgus, and if α₁/α₂ < 0, it illustrates the stem alignment is varus. In the lateral radiograph, if β > 0, it illustrates the stem alignment is retroverted, and if β < 0, it illustrates the stem alignment is anteverted

Fig. 3

Postoperative thigh pain timeline. The report of thigh pain can be categorized into 3 groups: “not at first, but later” group, “persist for some time and then stop” group, and “all the time” group. Correspondingly, there were 15% (10 of 68) hips, 53% (36 of 68) hips, and 32% (22 of 68) hips for each group, respectively

Fig. 4

Patient-reported thigh pain from the visual analog scale. A total of 18% of patients (45 hips) had mild thigh pain, 8% (20 hips) had moderate, and 1% (3 hips) had severe thigh pain