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Abstract

Objective

Femoral head necrosis (FHN) affects mostly young and active people. The most common operative therapy is core decompression (CD) with optional cancellous bone grafting (CBG). Because little information is available on the long-term results of these procedures, we investigated the effectiveness of CD and CD + CBG in patients with ARCO stage II FHN in terms of postoperative pain, range of motion, patient-reported outcome measures (Harris Hip Score, Hip Disability and Osteoarthritis Outcome Score, EuroQol 5D, and Short Form 36 Questionnaire), and disease progression.

Methods

We retrospectively compared 11 patients treated with CD alone 48.0 months (range, 26.3–68.5 months) postoperatively versus 11 patients treated with CD + CBG 69.2 months (range, 38.0–92.9 months) postoperatively. All patients were assessed according to a routine clinical protocol involving a clinical examination, questionnaires, and radiological imaging (X-ray and magnetic resonance imaging).

Results

The clinical and radiological results showed no significant differences between the two groups. Both interventions demonstrated equal results according to clinical scores.

Conclusions

Our data may encourage application of the less invasive technique of CD alone without CBG, which is more surgically demanding. Further prospective studies with longer follow-up are necessary to clarify the risk factors for therapy failure.

Keywords

Hip femoral head necrosis joint-preserving therapy core decompression cancellous bone grafting patient-reported outcome long-term outcome

Introduction

Femoral head necrosis (FHN) is a progressive disease. Disturbance of blood flow within the bone leads to increased intraosseous pressure, reduced intraosseous circulation to osseous structures, and finally aseptic necrosis of the bone.^1,2 Untreated, FHN results in secondary arthritis often necessitating total hip replacement (THR).³ The prevalence of FHN in Germany is 5000 to 7000 new cases per year, and that in the United States is about 10,000 to 20,000 cases per year.^4,5 Diagnosis of FHN accounts for 5% to 12% of THRs and is an important factor in health care systems worldwide.^1,5

Risk factors for reduced blood flow include traumatic conditions, steroid medications, alcohol and nicotine abuse, and metabolic diseases.^1,6,7 Steroid-induced osteonecrosis, similar to alcohol-induced osteonecrosis, is characterized by an increase in fat cells and marrow fat and thus a reduction in osteogenic cells.⁷ The increased intraosseous fat content leads to elevated intraosseous pressure and thus to venous stasis, diminished blood circulation, and finally ischemic necrosis.^8,9 Nicotine abuse causes vasoconstriction and thus decreased osteogenesis, bone volume, and vascular reactivity.^3,6 Various genetic disorders are also associated with avascular necrosis in general and FHN in particular, such as sickle cell anemia and coagulation abnormalities including factor V Leiden mutation, thrombophilia, and hypofibrinolysis.¹⁰

The ARCO classification of osteonecrosis is the most common classification used in the clinical setting. In addition to the extent of the lesion, which is classified as stages I to III, the localization of the lesion in stages II and III is categorized as grade A (medial), B (central), or C (lateral). Grade C has the worst prognosis among the three grades.^11,12 In 2019, the ARCO classification was revised. The final consensus resulted in the following four-stage system.

Stage I: X-ray examination is normal, but either magnetic resonance imaging or a bone scan is positive.

Stage II: X-ray examination is abnormal (subtle signs of osteosclerosis, focal osteoporosis, or cystic change in the femoral head), but there is no evidence of subchondral fracture, fracture in the necrotic portion, or flattening of the femoral head.

Stage III: X-ray examination or computed tomography scan reveals a fracture in the subchondral or necrotic zone. This stage is further divided into stage IIIA (early; femoral head depression of ≤2 mm) and stage IIIB (late; femoral head depression of >2 mm).

Stage IV: X-ray examination reveals evidence of osteoarthritis with accompanying joint space narrowing, acetabular changes, and/or joint destruction. The percent of area involvement is quantified by the crescent length and the percent of surface collapse and dome depression.¹³

In addition to ARCO staging, the size and location of the necrotic lesion are also important factors in the assessment of FHN. The percentage of the femoral head volume that is involved in the lesion is estimated by volume analysis techniques such as the Steinberg method, the Japanese Investigation Committee classification, the ARCO computed tomography-based classification, or the modified Kerboul method. Such estimation is particularly important for evaluating the risk of femoral head collapse and the need for surgery.

The Kerboul method was simplified in 2006. The arc of the necrotic portion on both the midcoronal and midsagittal images was measured, and the sum of these two angles was then calculated. There was a strong correlation between the combined necrotic angle and the risk of future collapse. None of the hips with a combined necrotic angle of ≤190° collapsed, all hips with an angle of ≥240° collapsed, and 50% of hips with an angle of 190° to 240° collapsed during the study period.¹⁴ These findings suggest that hips with a combined necrotic angle of ≤190° are at low risk, those with an angle of 190° to 240° are at moderate risk, and those with an angle of ≥240° are at high risk.

Core decompression (CD) is currently the most common surgical joint-preserving therapy.^15–18 The location of the necrotic area is detected with C-arm imaging. A guide pin is drilled from the proximal lateral femur, about 4 cm below the trochanteric ridge, into the lesion. In the same manner, multiple drillings with small Kirschner wires (K-wires) (usually 2.5 mm) are performed in a fan-shaped pattern. The sclerotic lamella of the necrotic area is broken up by drilling into the defect zone, leading to relief of intraosseous pressure^17,19,20; this results in significant pain reduction after the operation.^21–23 Nevertheless, the literature describes success rates widely ranging from 63.5% to 84.0%, but only in the early stages of the disease.^{6,8,16,17,19,24} Combined methods, such as bone grafting and mesenchymal stem cell transplantation, might be more effective than CD alone.^23,24 In autologous cancellous bone grafting (CBG), a core reamer (usually a 10-mm trephine) is drilled over the guide pin to create a 10-mm bone channel. The necrotic bone can then be removed and replaced by healthy cancellous bone.^17,19 This method is much more elaborate than the multiple drilling technique with K-wires alone. Nonetheless, no consensus has been reached regarding its effectiveness. Therefore, it is of great importance to gather accurate facts about the clinical outcomes of different treatments, especially for younger patients. Intraoperative X-rays of patients who have undergone CD and CBG are presented in Figure 1.

Figure 1.

Intraoperative X-rays of core decompression and cancellous bone grafting with (a) fan-shaped core decompression and (b) core reamer for cancellous bone grafting.

In this study, we investigated the effectiveness of two femoral head-preserving procedures for treatment of FHN: CD (with fan-shaped drilling) and CD + CBG. Furthermore, we aimed to correlate the postoperative pain level, range of motion (ROM), clinical scores, and disease progression.

Patients and Methods

This retrospective study involved all patients treated for FHN at the department of orthopedic surgery of a university hospital from 2006 to 2012. All symptomatic patients who visited during clinical consultation hours were included; asymptomatic patients were excluded. Indications for surgery were determined by two surgeons who performed the procedures (CD alone or CD + CBG). CD was performed with 2.5-mm K-wires in a fan-shaped pattern with multiple drillings as described in the Introduction.

In the performance of CBG, a 10-mm core reamer was drilled over the guide pin to create a 10-mm bone channel. The bone cylinder was excluded from the reamer, the necrotic bone was removed, and a healthy cancellous bone graft was taken out of the femoral neck and proximal femur and placed in the canal again and impacted. The standard postoperative treatment involved combination therapy with oral vitamin D and calcium for at least 6 weeks and partial weight-bearing with 20 kg for 6 weeks. The patients were advised to avoid high-impact activities for about 1 year. Physiotherapy was performed to strengthen the muscles and regain ROM.

Among 289 patients with FHN, 145 had advanced disease (ARCO stages III–IV) and therefore underwent THR. A total of 110 affected hips were treated with joint-preserving surgical therapy such as CD and autologous CBG or conservative therapy such as iloprost infusion. Among these 110 hips, 48 femoral heads developed aggravated disease despite therapy and therefore underwent THR. The other 62 femoral heads (57 patients) became consolidated; this group constituted the study cohort for differentiation of the most suitable femoral head-preserving treatment options.

The 57 patients (44 men and 13 women) were contacted in writing and by telephone call. Thirty patients (31 hips) were excluded for the following reasons: 15 patients did not answer; 2 patients declined visiting the hospital for examination because their hip condition was good; 8 patients declined participation without a stated reason; 1 patient declined participation because of current problems with his treated hip; 3 patients’ conditions had become significantly aggravated in the time between establishing patient contact and obtaining a definite diagnosis, and the patients underwent THR; and 1 patient died (Figure 2).

Figure 2.

CONSORT diagram of joint-preserving therapy.

Finally, 27 patients (31 treated hips) were enrolled in the study. The patients were categorized according to the ARCO classification.²⁵ Five patients had stage I disease, 23 had stage II, and 3 had stage III. No patients had systemic diseases such as sickle cell anemia, Gaucher disease, caisson disease, or autoimmune diseases (systemic lupus erythematosus, Sjogren’s syndrome, or scleroderma). Five patients reported subjective alcohol abuse, five reported subjective nicotine abuse, and eight reported a history of corticosteroid intake.

The patients were divided into two groups: the CD group and the CD + CBG group.

Finally, two additional inclusion criteria were applied, leading to further exclusion of patients. First, to obtain comparable results, only patients with ARCO stage II disease with a Kerboul angle of <200° were included. Second, the patients were matched according to sex and age in both groups. After application of these criteria, each group comprised 11 patients. The patients’ anthropometric data are shown in Table 1. The mean follow-up period of patients who underwent CD alone was 4.0 years (48.0 months; range, 26.3–68.5 months), and that of patients who underwent CD + CBG was 5.2 years (69.2 months; range, 38.0–92.9 months).

Table 1.

Comparison of patients’ anthropometric data between CD and CD + CBG groups.

	CD	CD + CBG
Male/female	7/4	7/4
Age, years	42.3 (28–54), SD = 8.9	41.9 (22–61), SD = 10.8
BMI, kg/m²	27.1 (21.2–33.5), SD = 3.5	27.2 (24.3–33.8), SD = 2.4
ARCO stage II	11	11

Data are presented as n or mean (range).

CD, core decompression; CBG, cancellous bone grafting; BMI, body mass index; SD, standard deviation.

The mean disease-free survival period for both groups was 4.93 years (59.1 months; range, 26.3–92.9 months).

All patient details were de-identified. The reporting of this study conforms to the STROBE guidelines.²⁶

Clinical protocol and scores

All patients were examined according to the same clinical protocol. First, physical examination of the hip included ROM and the documentation of contractions. ROM was recorded as the sum of flexion, adduction, abduction, and internal and external rotation with reference to the Harris Hip Score (HHS): 300° to 210° was considered an excellent result, 209° to 160° a good result, 159° to 100° a moderate result, and <100° a poor result.²⁷ Second, the patients were instructed to mark their pain level on a 10-mm visual analogue scale (VAS) for times of rest versus times of intense physical strain. Third, the radiological image evaluation was based on the ARCO classification. Therefore, plain radiographs and magnetic resonance images were assessed for staging. Finally, several patient-reported outcome scores were collected: HHS, Hip Disability and Osteoarthritis Outcome Score (HOOS), EuroQol 5D (EQ-5D), and Short Form 36 Questionnaire (SF-36).

Statistical analysis

The two groups were statistically compared using the t-test for the clinical test results and scores (HHS, HOOS, EQ-5D, and SF-36). When data showed a non-normal distribution and the t-test could not be used, the Mann–Whitney rank sum test was applied. All analyses were performed using SigmaPlot 11.0 (Systat Software Inc., San Jose, CA, USA). Statistical significance was defined as p < 0.05.

Results

The CD group obtained a mean overall ROM of 224.5° (range, 190°–265°), and the CD + CBG group obtained a mean overall ROM of 232.9° (range, 140°–280°). The t-test for ROM showed no significant difference between the two groups (Figure 3).

Figure 3.

Box plot of range of motion.

With respect to pain levels during rest, only one patient in the CD group reported moderate pain (VAS score of 5). In the CD + CBG group, two patients reported very mild pain (VAS score of 1) and one patient reported moderate pain (VAS score of 5). With respect to pain levels during intense physical strain, the patients in the CD group reported a moderate pain level of 3.3 (range, 0–8), and those in the CD + CBG group reported a pain level of 2.2 (range, 0–7). There was no significant difference in pain levels between the two groups (Figure 4).

Figure 4.

Box plot of visual analogue scale scores during physical strain.

In the CD group, postoperative staging with the ARCO classification using X-ray and magnetic resonance imaging examinations showed two hips with stage I disease, five hips with stage II, and four hips with stage IV, leading to a calculated mean ARCO stage of 2.5. In the CD + CBG group, six hips had stage II disease and five hips had stage III, also leading to a mean ARCO stage of 2.5 (Figure 5). Figure 6 shows the magnetic resonance images of one patient who had preoperative ARCO stage II disease and achieved conversion to ARCO stage I.

Figure 5.

Distribution of ARCO stages after femoral head-preserving therapy (number of cases).

Figure 6.

Magnetic resonance images of one patient with (a) preoperative ARCO stage II disease and (b) conversion to ARCO stage I disease.

All patients in both groups had ARCO stage II disease before therapy. Thirteen (59.1%) hips exhibited no progression in FHN (Figure 5). In the CD group, five (45.5%) hips remained at ARCO stage II, and two (18.2%) hips improved to ARCO stage I during follow-up. In the CD + CBG group, six (54.5%) hips remained at ARCO stage II. In the CD group, four (36.6%) hips showed worsening to ARCO stage IV with total radiological destruction of the femoral head. In the CD + CBG group, five (45.5%) hips showed worsening to ARCO stage III.

The CD + CBG group showed slightly better hip-specific scores (HHS and HOOS); however, the difference was not statistically significant (Table 2). The CD group achieved better results in the SF-36, but again without statistical significance. Overall, no statistically significant differences were found in any of the patient-reported outcome measures.

Table 2.

Evaluation of clinical scores.

Score	CD	CD + CBG
Harris Hip Score	87.7 (58–100), p = 0.362	93.2 (58–100), p = 0.362
HOOS	75.6 (37.2–95), p = 0.470	81.2 (37.2–100), p = 0.470
EQ-5D	79.1 (50–100), p = 0.788	80.9 (60–100), p = 0.788
SF-36 physical health	46.6 (21.2–56.2), p = 0.599	42.3 (20.1–57.3), p = 0.599
SF-36 mental health	53.2 (37.8–59.6), p = 1.000	49.8 (32.9–61.3), p = 1.000

Data are presented as mean (range).

CD, core decompression; CBG, cancellous bone grafting; HOOS, Hip Disability and Osteoarthritis Outcome Score; EQ-5D, EuroQol 5D; SF-36, Short Form 36 Questionnaire.

Patients who underwent conversion to THR after joint-preserving therapy are presented separately in Table 3. Figure 7 presents a comparison of time to failure (time between joint-preserving therapy and THR), especially for patients with ARCO stage II disease, between the CD and CD + CBG groups.

Table 3.

Baseline characteristics of patients converted to THR.

	CD	CD + CBG
Male/female	16/7	18/7
Age, years	50.4 (30–72), SD = 11.0	42.4 (29–73), SD = 10.9
ARCO stage
I	2	0
II	11	14
III	9	11
IV	1	0
Time between first joint-preserving therapy and THR, months	9.5 (1.3–26.8), SD = 7.0	11.3 (3.0–67.6), SD = 12.9

Data are presented as n or mean (range).

CD, core decompression; CBG, cancellous bone grafting; THR, total hip replacement; SD, standard deviation.

Figure 7.

Distribution of cases in the period between core decompression/cancellous bone grafting for ARCO stage II and total hip replacement (time to conversion). n = number of cases.

Discussion

We compared the two most common joint-preserving procedures, namely CD and CD + CBG, to clarify which provides better clinical outcomes.

Greater operative effort is required for CBG than for plain CD. Drilling for CD is usually performed with thin K-wires, causing only a small cortical defect, whereas a trephine (necessary for bone grafting) removes a larger part of the lateral cortical bone by insertion. This may cause structural instability and a resultant fracture of the femoral neck if partial weight-bearing is not enforced.²⁸ However, an advantage of CBG is the potential for greater efficiency of the healing process through new cancellous bone in the defect area.^28–30

Our study showed no significant difference in clinical outcomes between the CD and CD + CBG groups. Both interventions demonstrated equal results according to the clinical outcomes with low pain levels, almost normal mobility, and good quality of life based on the patients’ subjective perception. No conversion to hip arthroplasty during follow-up was necessary.

Most patients in both groups mentioned only mild pain at rest or during physical strain (VAS score of 3.3 in CD group vs. 2.2 in CD + CBG group) with a median follow-up of 48 months in the CD group and 69.2 months in the CD + CBG group. To our knowledge, no comparable long-term follow-up data regarding pain are available in the literature to date. Thus, our study has provided valuable data regarding good long-term pain reduction after CD and CD + CBG in patients with FHN.

Besides reduced pain, enhanced mobility is of great importance for patients. The extent of movement in every direction was summed to determine the overall ROM. We found only small differences in ROM between the two groups. The patients in the CD + CBG group showed slightly better results with a median ROM of 232.9° (range, 140°–280°; standard deviation, 34.0°) compared with 224.5° (range, 190°–265°; standard deviation, 24.96°) in the CD group. The available literature regarding follow-up after therapy for FHN describes only general “clinical improvement”^29,31,32 as a combination of reduced pain and improvement in everyday mobility. To our knowledge, our study provides the first detailed assessment of ROM with long-term follow-up.

We also evaluated several clinical scores, including hip-specific scores (HHS and HOOS) and general health scores (SF-36 and EQ-5D). Our analysis showed better hip-specific scores in the CD + CBG than CD group, but the difference was not statistically significant. Nonetheless, these findings are remarkable because of the long-term follow-up of 4 years in the CD group and >5 years in the CD + CBG group. Previous studies have revealed an HHS ranging from 72.25 to 88.42 at 12 months of follow-up.^29,32–34 Therefore, our study provides encouraging data regarding long-term outcomes after joint-preserving therapy.

In contrast to the hip-specific scores, the general health scores in the CD group were equal to or slightly better than those in the CD + CBG group. Our SF-36 results are slightly better than those reported in the literature (mental health aspect, 63.63–87.53; physical health aspect, 42.77–83.13).³⁴

Nonetheless, this discrepancy between the excellent hip-specific results (HHS and HOOS) and the rather poor self-assessment of general health (SF-36) is difficult to explain. It may be impacted by factors such as the patients’ different expectations, concomitant diseases, and medical history.

This study had three main limitations. The first limitation is the small number of patients; 22 hips were included in the study (11 in each group). Matching resulted in the exclusion of several patients. However, matching also led to a higher-powered study with a high level of homogeneity of the two groups. Including only patients with ARCO stage II disease avoided selection bias between different ARCO stages and facilitated matching according to age and sex. This early stage (II) is the most common stage at the time of initial diagnosis. Additionally, former studies have shown that stage II is the most promising stage for joint-preserving therapies.^35,36 Later in our study, we considered only patients who had received no preoperative treatments, such as iloprost infusion, which is often administered to patients with ARCO stage I disease. Therefore, these patients were also ineligible for inclusion.

Second, the literature provides evidence regarding different prognoses according to the size of the necrotic lesion. Even within the same ARCO stage, larger lesions tend to progress more rapidly whereas others seem to be well-maintained. In this study, we did not measure the volume of the necrotic lesion nor localize it. Nonetheless, in all femoral heads in the present study, the Kerboul angle was <200°. Thus, we observed small to medium-sized lesions with a rather good prognosis. Further studies involving larger Kerboul angles and a greater variety of lesion sizes and locations are needed and may produce different outcomes.

Third, the follow-up times were matched in both groups. However, it would have been ideal to compare the baseline clinical scores and pain levels. In this trial, comparability was determined by ARCO staging, similar Kerboul angles, matching of anthropometric patient data, and inclusion of only symptomatic patients. This helped to reduce selection bias, which is always a concern in retrospective studies. A prospective study is the gold standard for total exclusion of selection bias. Overall, the patients’ long follow-up time is remarkable. We evaluated the patients at an average of 4.6 years after therapy. At this time point, both interventions had resulted in good quality of life with low pain levels and almost normal mobility. A very important aspect was the absence of further progression that may have ended in THR.

Nevertheless, some patients with stage II lesions required THR after joint-preserving therapy. Before matching, 11 hips with ARCO stage II disease among the total cohort required THR at a mean follow-up of 9.5 months after CD. In the CD + CBG group, 14 stage II hips were converted to THR after a mean follow-up of 11.3 months. Approximately 50% of the stage II hips treated with CD showed long-term survivorship, compared with 44% in the CD + CBG group. These results are worse than those reported in the literature. Mont et al.³⁶ reported approximately 80% survivorship for patients with stage II necrosis 3 years after CD. This discrepancy may be due to the longer follow-up in our study.^6,36

Interestingly, the failures of joint-preserving therapies occurred rather early in our study (within 1 year on average). After a progression-free period of >1 year, deterioration of the treated hip seems less likely to occur. Nonetheless, an emphasis of our study was the high rate of femoral head survival after CD with or without CBG. A prospective study additionally considering end-point THR after joint-preserving therapy would certainly be of great interest.

In summary, both interventions were comparable with respect to the clinical outcomes and patients’ subjective perceptions. Our data may suggest that the less invasive technique of CD alone should be applied without CBG, the surgical performance of which is more highly demanding. Further prospective studies with longer follow-up are necessary to obtain more information about the disease course and risk factors for therapeutic failure.

Supplemental Material

sj-pdf-1-imr-10.1177_03000605231190453 - Supplemental material for Comparison of two joint-preserving treatments for osteonecrosis of the femoral head: core decompression and core decompression with additional cancellous bone grafting

Supplemental material, sj-pdf-1-imr-10.1177_03000605231190453 for Comparison of two joint-preserving treatments for osteonecrosis of the femoral head: core decompression and core decompression with additional cancellous bone grafting by Michael Woerner, Korbinian Voelkl, Christopher Bliemel, Felix Ferner, Markus Weber, Tobias Renkawitz, Joachim Grifka and Benjamin Craiovan in Journal of International Medical Research

Supplemental Material

sj-pdf-2-imr-10.1177_03000605231190453 - Supplemental material for Comparison of two joint-preserving treatments for osteonecrosis of the femoral head: core decompression and core decompression with additional cancellous bone grafting

Supplemental material, sj-pdf-2-imr-10.1177_03000605231190453 for Comparison of two joint-preserving treatments for osteonecrosis of the femoral head: core decompression and core decompression with additional cancellous bone grafting by Michael Woerner, Korbinian Voelkl, Christopher Bliemel, Felix Ferner, Markus Weber, Tobias Renkawitz, Joachim Grifka and Benjamin Craiovan in Journal of International Medical Research

Footnotes

Author contributions

MWO: planning, conception, and design of study; interpretation of data; writing of manuscript

KV: conception and design of study, acquisition and reporting of data, writing of manuscript

MWE: acquisition of data, analysis and interpretation of data, correction of manuscript

CB: correction of manuscript

FF: interpretation of data, correction of manuscript

TR: planning, conception, and design of study; supervision

JG: planning, conception, and design of study; supervision

BC: planning, conduct, reporting, conception, and design of study; correction of manuscript

Data availability statement

Original research data to support the results, tables, and figures presented in our manuscript are available upon reasonable request.

Declaration of conflicting interests

The authors declare that there is no conflict of interest.

Ethics approval and consent

This study was conducted after authorization by the Institutional Ethical Board of the Medical University of Regensburg (No. 14-101-0108). The study was performed in accordance with the ethical standards in the 1964 Declaration of Helsinki and carried out in accordance with regulations of the US Health Insurance Portability and Accountability Act (HIPAA). Written informed consent for participation in this investigation was obtained from all patients.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

ORCID iD

Michael Woerner

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