Clinical Outcomes of Lapidus Arthrodesis With Nitinol Staples for Hallux Valgus Correction

Abstract

Background:

This study evaluated postoperative outcomes following Lapidus arthrodesis (fusion of the first tarsometatarsal joint [TMT1]) using two nitinol staples for hallux valgus correction, focusing on fusion rate, reoperation rate, and patient satisfaction.

Methods:

A total of 60 cases undergoing Lapidus arthrodesis between June 2018 and June 2022 were analyzed with a median follow-up of 37 months (range: 15-64 months). All cases were treated using two nitinol staples (BME Elite^TM; DePuy Synthes) for TMT1 fusion. Among these, 38 cases involved additional foot procedures, while 22 cases had isolated TMT1 fusion. Data were collected from medical records, radiographs, and a telephone survey. The hallux valgus angle (HVA) and intermetatarsal angle (IMA) were measured preoperatively and postoperatively on weightbearing dorsoplantar radiographs. Functional outcomes were assessed using the Foot and Ankle Ability Measure–Activities of Daily Living (FAAM-ADL) subscale, and patient satisfaction was evaluated using a 4-point Likert scale.

Results:

The TMT1 fusion rate was 96.7% (58/60). The reoperation rate—including hardware removal, revision surgery for recurrence, and nonunion—was 16.7%. The staple breakage rate was 3.3%. The IMA improved from 15.8 to 8.9 degrees (P < .001), and the HVA improved from 37.5 to 17.3 degrees (P < .001). The average FAAM-ADL score was 81.7 out of 84, with 90% of patients reporting being very satisfied or satisfied.

Conclusion:

The Lapidus arthrodesis, fixed with nitinol staples, resulted in high rates of fusion and patient satisfaction.

Level of Evidence:

IV, retrospective cohort study.

Introduction

Arthrodesis of the first tarsometatarsal joint (TMT1) is an effective technique for treating hallux valgus deformities, offering three-dimensional correction and stabilization of the first ray. ²³ Popularized by Paul Lapidus, ²⁶ this procedure aims to reduce the first intermetatarsal angle (IMA), achieve rotational alignment, and restore sesamoid coverage. Over time, it has evolved with modifications to the surgical approach and the use of various implants, including crossed screws,^3,19,27 a lag screw and plate construct,^6,24 and alternatives such as staples.^2,16,21

Failure to establish fusion of the TMT1 joint results in nonunion, a commonly reported complication with rates up to 10%.^8,16,20,23 A specific nonunion rate for nitinol staples has not yet been established; however, a retrospective study by Mallette et al, ¹⁶ involving 36 patients, reported a rate of 8.3%. Nitinol staples are thought to exert continuous compression across the fusion site in biomechanical studies.^1,12,22 They should ease implantation, thereby reducing surgical time, and address hardware irritation problems with a low-profile design. However, proof of these assumptions is pending.

The objective of this study was to evaluate the success of Lapidus arthrodesis using two nitinol staples. Specifically, we aimed to report the fusion rate, reoperation rate, and staple breakage rate. Secondary objectives included evaluating patient-reported outcomes related to function and satisfaction.

Methods

The study was approved by the local ethics committee (reference number 35-293 ex 22/23).

This retrospective follow-up study evaluated medical records, radiographs, and data from a one-time standardized telephone survey conducted at a median of 37 months postoperatively (range: 15-64 months).

A total of 68 cases of Lapidus arthrodesis for hallux valgus deformity were performed using two nitinol staples (BME Elite^TM; DePuy Synthes). Surgical contraindications included conditions impairing adherence to postoperative care, and neurologic disorders. For this follow-up study, cases with concomitant arthritis of the midfoot or first metatarsophalangeal joint were excluded. The indication for Lapidus arthrodesis was either severe hallux valgus or moderate hallux valgus accompanied by first-ray hypermobility, assessed by a positive cross-glide test. ¹⁸ This test is defined as overt instability of the first tarsometatarsal (TMT1) joint during foot eversion, evaluated by the examiner while stabilizing the talonavicular joint. Surgeries were performed consecutively at our outpatient clinic between June 2018 and June 2022 by either a senior foot surgeon (P.H., M.O.) or by trainees (V.L., G.H.) under their direct supervision. Of the eligible cohort (n = 68), five patients were unreachable by phone, and three declined to participate, resulting in 60 cases being included in the final analysis.

Primary outcomes were assessed regarding bony fusion, reoperation, and staple breakage rate through chart review and radiographic assessment, with additional verification through a telephone survey to confirm or exclude the continuation of treatment elsewhere. Radiographic measures included the hallux valgus angle (HVA) and the first intermetatarsal angle (IMA), which were measured preoperatively and 2 months postoperatively on weightbearing dorsoplantar radiographs of the foot. The angles were measured by the author MM and reviewed by VL. Nonunion was diagnosed in patients presenting with persistent swelling and/or pain, along with radiographic signs such as staple breakage or an unhealed fusion site (Figure 2). Fusion (i.e., bony union) was diagnosed clinically by the absence of swelling and persistent pain, and radiographically by stable implant positioning and a continuous, harmonious appearance of the fusion site in two planes. The radiographs assessed were those routinely obtained at 2 months postoperatively, with additional images taken at 3 months in cases of delayed healing. CT or advanced radiographic scoring systems were not used, and fusion assessment relied solely on plain radiographs, which may limit diagnostic accuracy, particularly in asymptomatic patients. Hallux valgus recurrence was defined as a postoperative hallux valgus deformity accompanied by symptoms such as bunion discomfort, shoe conflict, or toe crowding. Operative time was defined as the interval between skin incision and wound closure.

Secondary outcomes included patient-reported outcome measures (PROMs), which were collected once via a standardized telephone survey. During this survey, two parameters were assessed: (1) Foot and Ankle Ability Measure–activities of daily living (FAAM-ADL) subscale, which comprises 21 items rated on a 4-point scale from “no difficulty” to “severe difficulty,” with a maximum score of 84 points indicating better function; ¹⁷ and (2) patient satisfaction, evaluated using a 4-point Likert scale with the categories: very satisfied, satisfied, moderately satisfied, and not satisfied.

Surgical Procedure

The procedure was performed under regional anesthesia with the patient in a supine position, utilizing a foot block. A single-dose antibiotic was administered, and a tourniquet was applied at 250 mm Hg. A medial incision was made from the first metatarsophalangeal joint (MTP1) to the TMT1 joint. The capsule of the MTP1 was opened, followed by a transarticular lateral release performed with a blade. Then, the lateral collateral ligament, sesamoid suspensory ligament, and capsular structures were detached using a McGlamry elevator. At the TMT1 joint, the capsule was incised, a Hintermann K-wire distractor was applied, and a careful, bone-sparing orthogonal osteotomy was performed at the base of the first metatarsal (MT1) for cartilage removal. A corrective osteotomy was then made at the medial cuneiform, aligned parallel to the hindfoot axis with adequate plantarization. Multiple drillings (2.0 mm) prepared the site for fusion. To correct the deformity, a temporary K-wire was placed medially into the MT1 head, allowing for rotation, lateralization, and slight plantarization of the first metatarsal. The K-wire was then advanced to temporarily fix the now aligned MT1 to the second and third metatarsals. Fluoroscopy confirmed the correction of the intermetatarsal angle and sesamoid coverage. Arthrodesis was established at the TMT1 with two 2-leg nitinol staples. The staples were placed in a crossed configuration, with one dorsally and the other medially across the joint (Figure 1). The final steps of the procedure included a medial bunionectomy at the MT1 head, followed by the closure of the capsule and skin. Postoperative management lasted 8 weeks: 2 weeks of nonweightbearing in a cork splint, 4 weeks of partial weightbearing (half body weight) in a surgical rigid sole shoe, and the final 2 weeks allowed full weightbearing in the surgical shoe. The big toe was splinted for 6 weeks to maintain soft tissue correction at the MTP1 joint.

Figure 1.

A case of hallux valgus correction with TMT1 fusion using nitinol staples. Preoperative dorsoplantar view with marked IMA and HVA (top left); dorsoplantar view at 8 weeks postoperatively showing good correction and two nitinol staples for TMT1 fusion (top right); corresponding lateral view at 8 weeks (bottom). HVA, hallux valgus angle; IMA, intermetatarsal angle; TMT1, first tarsometatarsal joint.

Statistics

Fusion, reoperation and staple breakage rate, as well as patient satisfaction were reported as ratios and percentages. Preoperative and postoperative measurements of the hallux valgus angle (HVA) and intermetatarsal angle (IMA) were analyzed using paired t tests, with statistical significance defined as a P value of less than .05. Statistical analyses were performed using SPSS software (IBM SPSS Statistics, version 25).

Results

Patient characteristics and surgical details are detailed in Table 1.

Table 1.

Patient Characteristics and Surgical Details (N = 60).

Parameter	Value
Sex: female/male, n (%)	51 (85)/9 (15)
Age, y, mean (SD)	55.8 (13.0)
Primary surgery or revision surgery, n (%)
Primary surgeries	53 (88)
Revision surgeries after hallux valgus recurrence	7 (12)
Procedure type, n (%)
Isolated TMT1 fusions	22 (37)
TMT1 fusions with additional procedures a	38 (63)
Intraoperative complications	0
Operative time (isolated TMT1 fusions), minutes, median (range)	41 (27-69)
Smoking status: smokers/nonsmokers, n (%)	17 (28)/43 (72)

Abbreviation: TMT1, first tarsometatarsal joint.

a

Additional procedures performed: Akin osteotomy, Chevron osteotomy, cheilectomy, Weil osteotomy, Hohmann procedure (condylar resection arthroplasty at the proximal interphalangeal joint), Stainsby procedure (base resection of the proximal phalanx with flexor tendon transfer).

The TMT1 fusion rate was 96.7% (58/60). Two cases of nonunion occurred, both associated with implant breakage (one staple per case). In both cases, the patients were smokers.

The main indications for reoperation were hardware irritation (8.3%; n = 5), hallux valgus recurrence (5%; n = 3), and TMT1 nonunion (3.3%; n = 2). The overall reoperation rate was 16.7% (10/60).

Both symptomatic cases of TMT1 nonunion were associated with a broken staple (Figure 2). Additionally, radiographic analysis identified two more cases with a broken staple at 2 and 3 months postsurgery, respectively. These two patients were symptom-free and achieved bony fusion of the TMT1 arthrodesis without further intervention despite the broken staple. The overall staple breakage rate was 3.3% (4/120).

Figure 2.

One of the two TMT1 nonunion cases. Preoperative radiograph (left); 8-week postoperative radiograph (middle) following TMT1 fusion with two nitinol staples; detail view of the fusion site at 6 months postoperative (right) showing nonunion and breakage of the medial staple. TMT1, first tarsometatarsal joint.

The IMA improved from 15.8 ± 3.5 degrees to 8.9 ± 4.3 degrees (P < .001). The HVA changed from 37.5 ± 8.2 degrees to 17.3 ± 8.5 degrees (P < .001). The average FAAM score was 81.7 ± 5.4 (maximum 84 points). The patient satisfaction rate was 90% (54/60), consisting of 40 patients who reported to be very satisfied and 14 to be satisfied. Additionally, six patients were moderately satisfied, whereas none were not satisfied.

Discussion

This retrospective study evaluated clinical, radiographic, and patient-reported outcomes following Lapidus arthrodesis using two orthogonally placed nitinol staples in a cohort of 60 patients with hallux valgus. With a median follow-up of 37 months, the procedure demonstrated a high fusion rate (96.7%) and favorable correction of the intermetatarsal and hallux valgus angles. Patient-reported outcomes collected via standardized telephone survey showed high functional scores and satisfaction rates. These findings suggest that nitinol staples may offer a viable fixation option for Lapidus arthrodesis; however, the absence of a comparison group and limitations in imaging and PROM data collection warrant cautious interpretation.

Previous studies have shown that nonunion rates are still of concern with Lapidus arthrodesis. Barp et al ² reported nonunion rates for various fixation systems: 9% for crossed screws, 5% for a lag screw with a locking plate construct, and 2% for a locking plate with an integrated compression screw within the plate. DeVries et al ⁸ showed a 10% nonunion rate for crossed screws in a comparative cohort, and 1.5% for a plate construct. Mallette et al ¹⁶ reported a nonunion rate of 8.3% after Lapidus arthrodesis with two nitinol staples in a cohort of 36 feet. To our knowledge, this is the only clinical data we can use for direct comparison given the similarities in technique and implants. Hence, our nonunion rate of 3.3% is relatively low. Both of our cases were associated with smoking, suggesting that nicotine use may be a contributing factor in our cohort, in line with its well-established role as a risk factor regardless of implant type.^4,5

Radiographs of the weightbearing foot were used to assess hallux valgus correction, and the improvements observed were consistent with prior studies. Importantly, the decision to perform Lapidus arthrodesis in this cohort was based on clinical TMT1 instability using the cross-glide test, ¹⁸ rather than specific angular thresholds. Although our patients had moderate deformities by radiographic criteria, others have argued that such cases may not require fusion. For example, Coughlin and Smith, in a prospective study with a mean IMA of 14.5 degrees, favored proximal osteotomy and distal soft tissue realignment. ⁷ Similarly, other authors have suggested IMA thresholds around 13 to 14 degrees may still be amenable to alternative procedures.^3,23

Reoperation after Lapidus is not uncommon, with the main indication being the surgical removal of prominent hardware when symptomatic. ¹⁶ We had an 8.3% rate of staple removal due to hardware irritation with the low-profile design of the staple bridge. Mallette et al ¹⁶ had a 22% rate of removal surgery due to painful nitinol staples, whereas Cottom and Vora ⁶ had a 17% rate of removal with lag screws and medial locking plates. Kane et al ¹³ identified a 6.5% rate of hardware removal and an additional 5% requiring revision surgery in more than 2500 Lapidus cases with screw fixation. In our study, nonunion revision surgery was infrequent, occurring in only two cases (3.3%). During nonunion revision, we removed the staples in both instances. In one case, the TMT1 was left unchanged, resulting in a stable, asymptomatic nonunion in a low-demand patient. In the other case, we inserted an allogeneic cortical bone screw (Shark Screw^®; Surgebright GmbH), which enabled pain-free, full weightbearing after 4 weeks, representing a novel approach to addressing nonunion. ¹⁵

Despite the goal of stabilizing the first ray with the Lapidus procedure, hallux valgus recurrence is possible. In our cohort, additional three feet (5%) required revision for deformity recurrence (Figure 3). Faber et al ¹⁰ reported an 8.7% recurrence rate after the Lapidus procedure at a 10-year follow-up, although no revisions were needed. In contrast, Galli et al ¹¹ reported a high objective radiographic recurrence rate of 38% in 127 primary Lapidus surgeries, with 24% of patients subjectively perceiving a recurrence and 9.5% requiring reoperation for it.

Figure 3.

A case with hallux valgus recurrence after Lapidus fusion and Akin osteotomy. A moderate hallux valgus deformity (IMA 14 degrees) with TMT1 instability in a male patient (A) was treated with two nitinol staples and an Akin osteotomy stabilized with a cannulated screw, achieving initial alignment with sesamoid coverage (B). At 6 weeks, slight sesamoid lateralization was seen (C), progressing to considerable lateralization and symptomatic hallux valgus recurrence at 1 year 8 months (D), requiring revision surgery (not shown). The TMT1 joint was fused; however, recurrence may be attributed to instability between the first and second rays at the midfoot (as seen in the gap), suggesting a problem with the indication and the chosen extent of fixation rather than an issue related to the staples. IMA, intermetatarsal angle; TMT1, first tarsometatarsal joint.

Regarding postoperative loading, our protocol included 2 weeks nonweightbearing in a splint, followed by 4 weeks partial weightbearing in a surgical shoe. With screws and screw plate constructs, other authors recommend nonweightbearing until consolidation (6-8 weeks),^8,19 others allowed weightbearing after 2 weeks or 4 weeks.^3,23,24 Notably, Prissel et al ²⁰ observed no significant difference in nonunion rates between early and delayed weightbearing in their retrospective review of various implant types. Our postoperative management after nitinol staple implantation is not yet scientifically proven; however, we do not deem the construct stable enough to allow full weightbearing immediately. Some restriction until 6 weeks after surgery should be considered in our opinion.

Staple breakage was noted in both cases of nonunion, with each involving a single broken staple, showing absent bony healing along with clinical symptoms of nonunion, mainly swelling and pain. Additionally, two other cases presented with a single broken staple on radiographs at 2 and 3 months postoperatively, but without clinical symptoms or need for intervention. These patients achieved uneventful healing and satisfactory outcomes. This is noteworthy, as metal breakage in plates or screws typically signals implant failure and often requires revision surgery. It is possible that the second staple maintained sufficient compression to support healing despite the breakage.

Secondary objectives were patient-reported measures. Although previous studies employed the AOFAS score,^5,9,10,14 we opted to use the FAAM. The FAAM has been recognized as a robust self-evaluation tool in hallux valgus surgery. ²⁵ Our average score of 81.7 of 84 points indicates high function. Patient satisfaction was 90%, comparable to other studies, ⁹ although the 4-point scale may be biased by factors beyond foot condition, such as waiting times and rehabilitation length.

Time efficiency is one practical advantage of staple fixation, as implantation is straightforward. In isolated Lapidus procedures, the median operative time in our cohort was 41 minutes, which we consider efficient. All procedures were performed in an outpatient setting under regional anesthesia (nerve block), highlighting the relevance of minimizing both tourniquet duration and total operative time.

The present study has several limitations, most notably its retrospective design. In addition to its retrospective design and modest sample size, no preoperative FAAM scores were collected, limiting conclusions about functional improvement. Union was diagnosed via plain radiographs without advanced imaging or quantitative scoring, which may have misclassified some cases. With a median follow-up of 37 months (range: 15-64 months), the potential for future revisions may not be fully captured. Three patients declined participation and five could not be reached, introducing potential selection bias. The inclusion of seven revision cases may add complexity and potentially confound the results when grouped with primary hallux valgus cases. The assessment of TMT1 instability relied mainly on the examiner’s clinical judgment. Additional forefoot procedures were performed in 38 cases, which may have affected outcome, especially patient-reported outcome measures. Only smoking status was assessed; other comorbidities and overweight/obesity were not considered. Subgroup analyses and multivariate testing, for example, regarding smoking or additional procedures, were not performed, introducing potential confounding bias. Recall bias may have influenced the accuracy of patient-reported outcomes collected retrospectively by telephone. Lateral radiographs were not analyzed, so potential first ray dorsiflexion deformity could not be assessed.

Conclusion

The current data support the feasibility of Lapidus arthrodesis using nitinol staples, with high fusion rates and favorable patient-reported outcomes.

Supplemental Material

sj-pdf-1-fao-10.1177_24730114251353789 – Supplemental material for Clinical Outcomes of Lapidus Arthrodesis With Nitinol Staples for Hallux Valgus Correction

Supplemental material, sj-pdf-1-fao-10.1177_24730114251353789 for Clinical Outcomes of Lapidus Arthrodesis With Nitinol Staples for Hallux Valgus Correction by Viktor Labmayr, Marlene Martinelli, Konstanze Huetter, Gloria Hohenberger, Patrick Holweg and Martin Ornig in Foot & Ankle Orthopaedics