Treatment of osteonecrosis of the femoral head with focal anatomic-resurfacing implantation (HemiCAP): preliminary results of an alternative option

Abstract

Background: The optimal treatment of osteonecrosis of the femoral head has not been established yet. The aim of this study was to report preliminary clinical results of focal anatomic-resurfacing implantation for the treatment of osteonecrosis of the femoral head.

Methods: Five patients (four male, one female) with seven surgical procedures, ages between 37 and 52 with an average age of 45.2 (+/- 7.2), diagnosed as femoral head avascular necrosis and who were unresponsive to conservative management or had failed previous surgical treatments were treated with a focal anatomic femoral head resurfacing between the years 2011-2012 and were retrospectively reviewed. Five patients with at least two years of follow-up, one left hip, two right hips, and two patients with bilateral hip surgery were included in this review. After safe surgical dislocation of the hip, full exposure of the femoral head was established. A focal-resurfacing implant matching patient anatomy and femoral head curvature was performed accordingly. Neither intraoperative or postoperative complications nor revision ensued. Visual analogue scores and Harris Hip Scores were recorded both preoperatively and at postoperative 2 years for all seven surgeries.

Results: The mean follow-up period was 26.6 +/- 3.8 months, with a range between 24-33 months. The mean visual analogue scores were 8.9 +/- 0.9 preoperatively and 2.3 +/- 1.0 postoperatively at year two (p = 0.017). Harris Hip Scores at postoperative follow-up were found to improve significantly from good to excellent scores (86.0 +/- 7.9), compared with preoperative poor scores (26.7 +/- 11.8) (p = 0.018). The clinical improvements in visual analogue scores (VAS) and Harris Hip Scores were also found to correlate with each other (p < 0.05).

Conclusions: In the present study, the alternative technique of focal anatomic hip resurfacing with HemiCAP® yielded preliminary successful results for the treatment of osteonecrosis of the femoral head. To the best of our knowledge, this is the first case series in the literature, reporting functional clinical results with the use of a focal anatomic-resurfacing implant for the treatment of focal femoral head osteonecrosis.

Figure 1

Preoperative X-ray. Anteroposterior pelvis X-ray demonstrating bilateral ON of the femoral head.

Figure 2

Preoperative MRI scan. T1-weighted coronal MRI scan demonstrating bilateral ON of the femoral head.

Figure 3

Surgical step 1. Following determination of the borders of the affected softened cartilage overlying osteonecrotic area and femoral head osteoplasty (if necessary due to impingement), a K-wire is passed through the sizing jig, into the center of the predetermined osteonecrotic area, which was debrided by using a power drill, with simultaneous lavage.

Figure 4

Surgical step 2. Implantation of the tapered titanium screw securely by the screwdriver, after proper taping over the guide K-wire and sizing of the medial, lateral, anterior, and posterior contours with the contact probe.

Figure 5

Surgical step 3. Placement of the anatomically fit sized, 35 mm diameter final implant with slight tapping with a mallet, after trialing and surface reaming. Final view of tapered interlocked CoCrMo articular-resurfacing component, approximately 0.5 mm below the peripheral healthy articular cartilage surface.

Figure 6

Intraoperative fluoroscopic view. Intraoperative fluoroscopic view showing a properly placed implant (HemiCAP®, Arthrosurface, Franklin, MA) with preservation of the joint space after reduction of the joint and final repair of the trochanteric osteotomy with two 4.5-mm cortical screws.

Figure 7

Postoperative X-rays. X-rays at postoperative second years of a 48-year-old male patient. These radiographs show the preservation of the joint spaces without loosening of the implants bilaterally. The screws were removed because of irritation in this patient.

Figure 8

Postoperative X-rays. X-rays of a 37-year-old male patient at postoperative 24^th months.

Figure 9

Mean VAS and Harris Hip Scores. Mean values (+/− SD, longitudinal lines) of preoperative (purple bar) and postoperative second year (green bar) VAS and Harris Hip Scores (VAS = visual analogue score, HHS = Harris Hip Score, preop. = preoperative, postop. = postoperative).