Comparison of outcomes according to fixation technique following the modified Ludloff osteotomy for hallux valgus in patients with rheumatoid arthritis

This retrospective case-controlled study was conducted after approval from the Institutional Review Board at Hanyang University Hospital (HYUH 2016–03-008), and all patients provided their informed consent. Ninety-two patients with RA (108 feet) underwent HV surgery at the Hanyang University Medical Centre between March 2005 and December 2014. Excluding the patients who underwent first MTP joint fusion, first MTP joint resection arthroplasty, or first metatarsal distal osteotomy, 29 patients (31 feet) with at least 1 year of follow-up after modified Ludloff osteotomy were included as subjects.

In the present study, we performed joint-preserving HV surgery only in patients showing minimal erosion of the first MTP joints (below Larsen grade 2) [11]. Moreover, we performed the modified Ludloff osteotomy when moderate-to-severe HV deformities were present. We used to fix the modified Ludloff osteotomy sites using two Barouk screws (Depuy International, Leeds, England) until December 2010. However, after observing a loss of correction in several RA patients, since January 2011, we implemented the augmented plate fixation technique, which involves the use of a metal plate in addition to the two Barouk screws for fixation of osteotomy sites.

During HV surgery for patients with RA, the fixation technique performed with two Barouk screws was used to fix the osteotomy sites in 15 patients (15 feet, Group S), while the augmented plate fixation technique was used in 14 patients (16 feet, Group P). The baseline data from these two groups are summarised in Table 1.

The surgery was performed by one senior surgeon (IHS). A longitudinal incision (approximately 7 cm in length) was made on the medial side of the bunion and the shaft of the first metatarsal in order to remove the bunion using a saw in a direction parallel to the longitudinal axis of the first metatarsal shaft. We used a modified version of Ludloff osteotomy, which involved the following. A longitudinal oblique osteotomy was performed from the plantar-distal aspect of the first metatarsal shaft immediately proximal to the sesamoid complex and directed to the dorsal-proximal aspect. At the end of osteotomy, a vertical step-cut osteotomy was made on the dorsal cortex, which gave additional stability and prevented excessive shortening with its buttressing effect to the distal fragment. After laterally transposing the distal fractured fragments of the first metatarsal to obtain 1–2 IMA to approximately 5°, the osteotomy site was fixed using two Barouk screws. Starting January 2011, the osteotomy site was augmented in RA patients using an LCP Compact Hand 2.0-mm or 2.4-mm (Synthes, Oberdorf, Switzerland) on the medial side, in addition to the Barouk screws.

The hallux valgus angle (HVA) was corrected by making an additional incision (approximately 2 cm in length) in the first web space, and distal soft-tissue realignment was subsequently conducted. If the HVA correction was insufficient or if excessive tension was applied on the distal soft tissues, an additional Akin osteotomy was performed as needed. Lesser toe deformities were corrected selectively by resection arthroplasty or Weil osteotomy based on the severity and flexibility of the deformity and the extent of MTP joint erosion.

Immediately after surgery, non-weight-bearing plain radiographs were obtained, and all patients were subsequently allowed to place weight on their heels while wearing postoperative shoes beginning 1 week after surgery. At 3 weeks after surgery, sutures were removed while the patient was in the outpatient clinic, and full weight-bearing was allowed when wearing regular shoes at 6 weeks postoperatively. To maintain the corrected hallux position, patients were advised to keep their dressing bandage in place for 6 weeks after surgery.

All patients who underwent HV surgery were evaluated preoperatively and at 6 weeks, 3 months, 6 months, and 12 months postoperatively. These visits were followed by an annual check-up to measure the American Orthopaedic Foot and Ankle Society (AOFAS) hallux metatarsophalangeal-interphalangeal score and patients’ subjective satisfaction as well as to obtain weight-bearing plain radiographs.

For clinical evaluation, preoperative and final follow-up AOFAS scores of the two groups were compared. When comparing the AOFAS scores, we analysed the total scores as well as the scores for each subscale, which included pain (40 points), function (45 points), and alignment (15 points). In addition to the AOFAS scores, the level of patients’ subjective satisfaction was recorded at the final follow-up for comparison and categorised into “excellent”, “good”, “fair”, or “poor” [12].

For radiological evaluation, HVA, 1–2 IMA, and sesamoid position were compared between the two groups preoperatively, immediately after surgery, 6 weeks and 6 months postoperatively, and at the final follow-up. The HVA was measured as the angle between the line connecting the centre of first metatarsal’s proximal articular surface to the centre of the first metatarsal head and the line connecting the midpoints of proximal and distal articular surfaces of the proximal phalanx [13]. The 1–2 IMA was measured as the angle between the line of first metatarsal bone and the line bisecting the second metatarsal shaft. The sesamoid positions were assessed using the method described by Hardy and Clapham; they were graded from I to VII based on the positional relationship between the medial sesamoid and the longitudinal axis of first metatarsal (I, most medial; VII, most lateral) [14].

To evaluate the degree of fixation stability at the osteotomy site for each fixation technique, the absolute values of angle variations were compared by measuring the angle of altered margin of the lateral cortex (AMLC) and 1–2 IMA, immediately and 6 weeks after surgery. The angle of AMLC was defined as the angle between the proximal and distal lateral cortices on the osteotomy site (Fig. 1), while a loss of correction was defined when the 1–2 IMA and angle of AMLC measured 6 weeks after surgery changed by more than 5° from those measured immediately after surgery. We could not measure the angle of AMLC after 6 weeks following surgery because the angle was not accurately identified due to united osteotomy sites. Furthermore, the HVA recurrence rates of the two groups at the final follow-up were compared. Recurrence was defined as HVA ≥20° [15].

The bone mineral density (BMD) was compared between patients with correction loss at the osteotomy site and those with no loss of correction. Hanyang University Medical Centre has a special institution for RA patients (Hanyang University Hospital for Rheumatic Disease), and most RA patients who visit the department of orthopaedic surgery for forefoot surgery were transferred from this institution. Areal BMD measurement was annually performed for the lumbar vertebra and femoral neck in most RA patients using dual energy X-ray absorptiometry (DXA) (Discovery QDR, Hologic, Bedford, MA, USA) for the evaluation of osteoporosis at the department of rheumatology. Therefore, most RA patients who underwent forefoot surgery at our institution had DXA performed within 1 year. Of the preoperative measurements of femoral neck BMD from both sides, we used the lower values for analysis.

For radiographic measurements, two orthopaedic surgeons (YHJ, YSS) who did not participate in the surgeries, measured radiological parameters using the PACS π view star (Infinitt, Seoul, Korea) digital measurement program at two sessions with a 2-week interval in between, and mean values of the measurements were used for analysis. To evaluate intra- and inter-observer concordance, intra-class coefficients (ICC) and Kappa coefficients, respectively, for HVA, 1–2 IMA, sesamoid position, and angle of AMLC were calculated.

In addition to the clinical and radiological outcomes, complications, including implant irritation, infection, non-union, deep vein thrombosis, first MTP joint arthrosis, and delayed wound healing were compared between the two groups.

No statistically significant difference was found between the two groups in the following categories: age (p = 0.069), sex (p = 1.000), body mass index (p = 0.843), side (p = 0.379), postoperative outpatient follow-up duration (p = 0.080), duration of RA (p = 0.226), preoperative C-reactive protein levels (p = 0.572), preoperative erythrocyte sedimentation rate (ESR) levels (p = 0.358), preoperative Disease Activity Score using 28 joint counts based on ESR (DAS28-ESR) (p = 0.834), preoperative Larsen grade of the first MTP joint (p = 1.000), whether Akin osteotomy was performed (p = 0.394), whether a lesser toe procedure was performed (p = 0.376), operation time (p = 0.163), and distal metatarsal articular angle (DMAA) (p = 0.545). However, femoral neck BMD and T-score were significantly lower in Group P than in Group S (p = 0.043, p = 0.039) (Table 1).

AOFAS scores measured before surgery and at the final follow-up are summarised in Table 2. The total AOFAS scores measured at the final follow-up were significantly better in both groups compared to those obtained before surgery (all p < 0.001). The two groups did not differ significantly in terms of the preoperative and final follow-up total AOFAS scores (p = 0.861; p = 0.096). Similarly, significant differences were not observed in the pain and function subscales of the AOFAS scores between the two groups. However, Group P scored significantly higher in the alignment subscale at the final follow-up (p = 0.004).

Subjective patient satisfaction levels measured at the final follow-up in the two groups were as follows: five Group S patients (33%) and eight Group P patients (57%) indicated that their satisfaction levels were “excellent”; five Group S patients (33%) and four Group P patients (29%) reported “good” satisfaction levels; three Group S patients (20%) and two Group P patients (14%) responded with “fair” satisfaction levels; and only two patients (13%), both of whom were in Group S, experienced a “poor” level of satisfaction.

The intra-observer reliabilities for HVA, 1–2 IMA, sesamoid position, and AMLC angle showed an ICC of 0.87 (95% confidence interval [CI], 0.82–0.92), ICC of 0.92 (95% CI. 0.86–0.98), kappa coefficient of 0.82 (95% CI, 0.74–0.90), and ICC of 0.80 (95% CI, 0.70–0.88), respectively, demonstrating outstanding reliability. Inter-observer reliability for these same variables showed an ICC of 0.83 (95% CI, 0.75–0.91), ICC of 0.88 (95% CI, 0.82–0.94), kappa coefficient of 0.76 (95% CI, 0.69–0.82), and ICC of 0.72 (95% CI, 0.64–0.80), respectively, further confirming the reproducibility of results.

Changes over time in the HVA, 1–2 IMA, and sesamoid position in Group S and Group P are illustrated in Figs. 2, 3, and 4. HVA, 1–2 IMA, and sesamoid position significantly improved in the two groups at final follow-up compared to those measured before surgery (all p < 0.001). HVA (p = 0.456, p = 0.727) and sesamoid position (p = 0.259, p = 0.488) measured before surgery and at the final follow-up were not significantly different between the two groups (Table 3). Regarding 1–2 IMA measured before surgery, no significant difference was observed between the two groups (p = 0.066); however, significant differences were found at the final follow-up (p = 0.001). Using the mixed model analysis, no difference by time interaction was found for postoperative HVA (p = 0.662) and sesamoid position (p = 0.824); however, a significant difference by time interaction was found for postoperative 1–2 IMA (p = 0.011) between the two groups (Figs. 2, 3, and 4). The pairwise comparisons to examine differences in 1–2 IMA between groups at each of the follow-up points where 1–2 IMA measurement was immediately performed after surgery were not significantly different between the groups (p = 0.748). However, at six weeks after surgery, the mean 1–2 IMA of Group S was significantly higher than that of Group P, and that difference was maintained until the final follow-up (significance level was corrected to 0.0125 with the Bonferroni method; p = 0.004 at 6 weeks, p = 0.002 at 6 months, and p = 0.004 at the final follow-up).

An analysis of the fixation stability of osteotomy sites showed that mean variations in the 1–2 IMA and angle of AMLC measured immediately and 6 weeks after surgery in Group S were 3.3° and 4.7°, respectively, and 0.9° and 2.1°, respectively, in Group P (p = 0.001, p = 0.024). A loss of correction was observed in five feet in Group S (33%) and 0 feet in Group P (0%) (p = 0.018) (Figs. 5, 6). There were no significant differences in HVA, 1–2 IMA, and sesamoid position measured before and immediately after surgery between the correction loss and correction maintenance subgroups within Group S (Table 4). The five feet in correction loss subgroup within Group S showed significantly lower BMD values compared to those for the remaining 10 feet in which no loss of correction occurred (p = 0.023) (Table 5). There were no significant differences in BMD values between Group P and the correction loss subgroup within Group S, and no patients in Group P showed correction loss (Table 5).

Two patients (13%) in Group S reported persistent symptoms of bunion pain and symptomatic HV, but no such HV symptoms were reported in Group P. Implant irritation caused by plates occurred in five feet (31%) in Group P, and consequently, one patient underwent surgery for implant removal. Other complications such as non-union, infection, deep vein thrombosis, and first MTP joint arthrosis were not observed. Both groups had one patient each who showed delayed wound healing as the normal healing process was not achieved within 3 weeks, but these wounds healed after conservative treatment.