Abstract
Metatarsal head resection is a common and standardized treatment used as part of the surgical routine for metatarsal head osteomyelitis. The aim of this study was to define the influence of the amount of the metatarsal resection on the development of reulceration or ulcer recurrence in patients who suffered from plantar foot ulcer and underwent metatarsal surgery. We conducted a prospective study in 35 patients who underwent metatarsal head resection surgery to treat diabetic foot osteomyelitis with no prior history of foot surgeries, and these patients were included in a prospective follow-up over the course of at least 6 months in order to record reulceration or ulcer recurrences. Anteroposterior plain X-rays were taken before and after surgery. We also measured the portion of the metatarsal head that was removed and classified the patients according the resection rate of metatarsal (RRM) in first and second quartiles. We found statistical differences between the median RRM in patients who had an ulcer recurrence and patients without recurrences (21.48 ± 3.10% vs 28.12 ± 10.8%; P = .016). Seventeen (56.7%) patients were classified in the first quartile of RRM, which had an association with ulcer recurrence (P = .032; odds ratio = 1.41; 95% confidence interval = 1.04-1.92). RRM of less than 25% is associated with the development of a recurrence after surgery in the midterm follow-up, and therefore, planning before surgery is undertaken should be considered to avoid postsurgical complications.
Diabetic foot is a serious complication of diabetes mellitus that occurs in approximately 3% to 4% of patients with diabetes around the world. 1 In some cases, the presence of a foot ulcer precedes a minor or major amputation. Peripheral arterial disease (PAD) and diabetic foot infections (both soft tissue infections and osteomyelitis) have been described as being the main causes of limb loss. 2
Although benefits of surgery for soft tissue infections have been demonstrated, especially in necrotizing soft tissue infections, the best therapy for diabetic foot osteomyelitis is still a matter of debate. 3 One approach for treating osteomyelitis is the combination of surgery and systemic antibiotics. Some studies have demonstrated that conservative surgery can treat bone infections, preserving the anatomy and function of the foot instead of resorting to minor amputations, such as ray or transmetatarsal amputations.4,5
The plantar surface is a common location of diabetic foot ulcers, especially in the forefoot where there is a protrusion of the metatarsal heads. Metatarsal head resection is a common and standardized treatment that is used as part of the surgical routine for metatarsal head osteomyelitis. 6 Surgery should be considered when the following indications are found: the metatarsal head shows damage in a plain X-ray, bone can be observed at the bottom of the ulcer, the foot ulcer is associated with rigid deformity, the bone infection is associated with spreading soft tissue infection, and when previous antibiotic therapy with appropriate offloading has not shown any improvement over the previous 6 weeks.7,8
Some studies9-11 have suggested that metatarsal head resection should also be used to decrease the peak plantar pressure of the forefoot, thus avoiding a possible recurrence, to allow faster healing of the plantar foot ulcer.
Griffiths and Wieman, 6 in 1990, described metatarsal head resection in diabetic patients, and they defined it as a bone osteotomy at the surgical neck of the metatarsal, from which the metatarsal head is removed. The most common complication associated with this procedure was a pressure transfer lesion. This condition will move the peak pressure to the adjacent metatarsal joints, and consequently, a new ulcer may develop.12,13
Another concern that has, until now, not been adequately investigated is the possibility of ulcer recurrences at the same area of the surgery, 14 especially when the metatarsal head resection was not located at the surgical metatarsal neck. Removing more or less of the distal portion of the infected metatarsal may be associated with an increased probability of reulceration or recurrences after surgery. When recurrences have occurred, in some cases, revision surgery was required. Nevertheless, in the majority of the previous studies, reulceration and ulcer recurrence were not evaluated as being different outcomes and were instead assessed as being the same complication.15-17
Until now, the surgical procedure for removing the metatarsal head has not been well defined, and often the surgeon will not know how much of the bone has to be removed. There is no clear indication regarding the metatarsal amputation level in the literature, 16 and knowledge of the postsurgical implications of whether the bone is cut above or below the surgical neck of the metatarsal is unknown.
The aim of this study was to define the influence of the amount of the metatarsal resection on the development of reulceration or ulcer recurrence in patients who suffered from plantar foot ulcer and underwent metatarsal surgery.
Patients and Methods
Between October 2011 and October 2013, 50 patients underwent metatarsal head resection surgery to treat diabetic foot osteomyelitis at the Diabetic Foot Unit of the Complutense University of Madrid, Spain. Of these, there was no prior history of foot surgeries in 35 patients, and these patients were included in a prospective follow-up over the course of at least 6 months in order to record reulceration or ulcer recurrences (see flow chart in Figure 1).
Flow chart of the process of inclusion of patients in the present study.
Inclusion criteria were as follows: diabetes patients aged >18 years, neuropathic ulcers complicated by osteomyelitis, ability to attend during the follow-up period, and agreeing to be included in the study by means of written consent.
Exclusion criteria were as follows: patients with previous surgery or previous amputation, inability to measure the metatarsal length due to significant damage to the metatarsal head, patients suffering from PAD, 18 previous history of metatarsal fracture or Charcot foot, and patients who did not understand the purpose of the study or refused to be included.
The demographic and clinical characteristics of the study population are shown in Table 1.
Baseline Clinical Data of Subjects (N = 35).
Abbreviations: SD, standard deviation; HbA1c, glycated hemoglobin.
The diagnosis of osteomyelitis was established on the basis of a combination of a probing-to-bone test and plain X-rays, as previously published. 19 The probe-to-bone test was performed using metal forceps (Halsted mosquito forceps), and the result was considered positive when the researcher felt a hard or gritty surface. We considered the plain X-rays (2 standard views) “positive” for osteomyelitis if they showed cortical disruption, periosteal elevation, a sequestrum or involucrum, or gross bone destruction.
The neurological examination was conducted using a Semmes-Weinstein 5.07/10 g monofilament (Novalab Ibérica, Alcalá de Henares, Madrid, Spain) and a Horwell’s biotensiometer (Novalab Ibérica). Neuropathy was diagnosed in patients who did not feel 1 of the 2 tests. 20 PAD was diagnosed if the patient met the following criteria: absence of both distal pulses and/or ankle brachial index <0.9. 18
All patients included in the present study underwent a metatarsal head resection according to the previously described surgical procedures.6,14 The same surgeon (JLM) performed all the procedures.
Resection of the metatarsal head approach could be performed through a dorsal linear incision centered directly on the metatarsal head. Once the metatarsal head was exposed, the surgeon located the site for the osteotomy. The base of the proximal phalanx was removed where it was infected. The dorsal approach was closed primarily, and the ulcer was then allowed to heal by secondary intention.
Anteroposterior plain X-rays were taken before and after surgery using the following protocol: with the patient standing, the plantar aspect of the foot was placed on the cassette in a parallel position with the other foot. The X-ray beams were centered with an inclination angle of 15° on the foot in an anteroposterior position with an anode film distance of 100 cm. 21 The same radiologist from our department took all the radiographs.
The Kodak Quality Control software, POC 360 (Eastman Kodak Company, Rochester, NY), was used to perform the metatarsal length measurements. We measured the portion of the metatarsal head removed in order to compare the influence of the amount of bone removed on reulceration and recurrence during the follow-up. We calculated the amount of metatarsal removed during the surgery as follows:
Maximum length of the metatarsal (MLM) was measured before the surgery and was considered to be the distance between the tip and the most distal point of the head. 22
Postsurgical length of the metatarsal (PLM) was measured after the surgery and was considered to be the distance between the tip and the most distal point of the resection surface.
Length of the metatarsal resection (LMR) was the difference between the MLM and the PLM (Figure 2).
Technique to measure the maximum length of metatarsal (MLM), postsurgical length of metatarsal (PLM), and length of the metatarsal resection (LMR).
Finally, the resection rate of the metatarsal (RRM) was calculated by multiplying the LMR by 100 and dividing by the MLM. We classified the patients according to the RRM performed into the first quartile (RRM less than 25%) and the second quartile (RRM between 25% and 50%).
During the first 48 hours after surgery, weight bearing was not allowed. Afterwards, the patients were allowed to bear weight on the operated foot while using 3 layers of 5-mm-thick felted padding, each placed behind the rest of the metatarsal heads, and a removable cast walker, until the wound completely healed. 23 Healing was defined as the complete epithelialization of the ulcer and/or the surgical wound created while treating the infection.
Once the ulcer was healed, the patients underwent biomechanical evaluation using an F-Scan (Rsscan International, Olen, Belgium). 24 A customized insole was applied and an extra-depth shoe was prescribed. 25 The patients were followed monthly according to the recommendations of the International Working Group of the Diabetic Foot during the follow-up period. 26 The revisions were made by a podiatrist who specialized in diabetic foot.
The main outcome variables evaluated in the present study were reulceration and ulcer recurrence, as well as their relationship to RRM.
Reulceration was defined when, after metatarsal resection, a new ulcer appeared that was located under the head of a metatarsal that was different from the one previously operated on.
Ulcer recurrence was considered to be a new ulcer that occurred after healing and was located beneath the plantar surface where the metatarsal head was removed.
Statistical analysis was performed using SPSS version 19.0 for Windows (SPSS Inc, Chicago, IL). A Student’s t test was performed for the independent samples to compare the averages of the quantitative variables. The χ2 test was used to identify differences in the qualitative variables. Odds ratios and their 95% confidence intervals were determined using univariate analysis. A difference of less than 5% was assumed to be significant for a type I error (P < .05).
Results
Thirty-five patients were included in the study according to the inclusion and exclusion criteria. Five patients were excluded during the follow-up; 2 of the patients were excluded because several metatarsal head resections were removed during the surgery, and the other 3 patients were excluded because they dropped out before completing 6 months of follow-up. In all, 30 were included in the prospective analysis.
The median follow-up time was 22 months (interquartile range [IQR] = 10-24 months; minimum = 6 months, maximum = 24 months). During the follow-up, 14 (46.7%) patients suffered from reulceration, and 5 (16.7%) patients suffered from ulcer recurrence. The median reulceration time was 1 month (IQR = 0.5-4 months; minimum = 0.25, maximum = 12), and the median ulcer recurrence time was 12 months (IQR = 4.75-14.5 months; minimum = 2, maximum = 17).
The mean MLM in all patients was 7.23 ± 0.91 cm, and the mean LMR was 1.94 ± 0.75 cm, which was equivalent to 26.5% of the MLM. The mean RRM in all patients was 27.01 ± 10.22%. We did not find any statistical differences between the median RRM in patients suffering from a reulceration and those that did not (30.44 ± 12% vs 23.97 ± 7.31%; P = .09). However, we found statistical differences between patients who had an ulcer recurrence and patients without recurrences (21.48 ± 3.10% vs 28.12 ± 10.8%; P = .016).
Seventeen (56.7%) patients were classified in the first quartile of RRM, which had an association with ulcer recurrence (P = .032; odds ratio = 1.41; 95% confidence interval = 1.04-1.92). Thirteen patients (43.3%) were classified in the second quartile, and they did not show an association with ulcer recurrence (P = .49). No patients were included in the third and fourth quartiles.
Discussion
According to our results, reulceration and ulcer recurrences were common complications in patients undergoing metatarsal head resection (19 patients; 63.3%). This result is even higher than those previously published by our group, 12 although in the present study, we analyzed only the patients who underwent their first metatarsal resection surgery. It seems that metatarsal head resection is associated with a high risk of developing new foot ulcers.
When we divided the events into reulceration and ulcer recurrences, we found that reulceration was an early complication compared to recurrence. The median time for recurrence was 12 months, but only 1 month for reulceration.
Recurrences showed an association with patients who underwent an RRM of less than 25% (quartile 1). The mean RRM was less in patients who underwent a recurrence (21.48%) than in patients experiencing reulceration (30.44%). Insufficient RRM triggers ulcers in the same area, and excessive RRM may be one of the reasons that lesions transfer to another metatarsal head.
We did not find any previous studies in which the amount of bone removed was investigated. However, an ulcer recurrence after bone resection could be the cause for ray amputation.27,28 Kadukammakal et al 17 did not find any differences between re-amputation rates after the first metatarsal resection, whether or not the osteotomy was performed at the surgical neck. Other studies15,29 showed re-amputation rates of 9% and 42.4%, respectively, after the first ray amputation, but these reports did not include an evaluation of the influence of the amount of bone removed by the surgical procedure.
Some authors 11 have suggested that metatarsal head resection could help with the offloading after surgery, thus avoiding the development of a new ulcer. In fact, it was considered an advantage when surgery was chosen as the therapy for resolving diabetic foot osteomyelitis. However, according to our results, surgeons should better plan the amount of bone that must be removed. Normally, surgeons are only concerned with removing all of the infected bone, and they are not aware of possible alterations of the metatarsal parable and its influence on reulceration or recurrence.
We think that it is important to analyze reulceration and ulcer recurrence separately, because the etiology of both events may be different. It is likely that early recurrences are associated with unresolved osteomyelitis due to residual bone infection, but later recurrences may be associated with insufficient bone resection. We do not think that ulcer recurrence is due to unresolved infections, because the median time for recurrences was 12 months, which is enough time to consider the osteomyelitis to have been cured. 30
The identification of the metatarsal surgical neck helps avoid recurrences when an osteotomy is performed in this area. However, until now, the amount of bone that must be resected has been a personal decision. According to our results, removing more or less of the metatarsal may be associated with ulcer recurrence after surgery. For this, the recommendation for metatarsal head cut off was considered to be 25% of the metatarsal. On the other hand, reulceration could be associated with transfer lesions due to inappropriate, insufficient, or noncompliant offloading.
The present study has several limitations. We did not quantify the deviation in the sagittal plane of the metatarsal in the lateral view on the plain X-ray, since it has been reported that such deviations may be responsible for plantar lesions under some circumstances. We also did not analyze whether or not the dorsal or plantar approach for metatarsal resection could influence the amount of bone removed.
The strength of the current study is that it is the first study in the literature to analyze the causes of ulcer recurrence after a metatarsal head resection. The recommendations for the amount of bone that must be removed could help avoid these events. Ulcer recurrence has been considered the cause of minor amputation and revision surgery.8,15
In conclusion, an RRM of less than 25% is associated with the development of a recurrence after surgery in the midterm follow-up. Before performing a metatarsal head resection, the surgeon should calculate 25% of the length of the metatarsal to determine the amount of bone to be resected and to avoid postsurgical complications.
Footnotes
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.